#next contents index first

   W3C

Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification

W3C Recommendation 07 June 2011, edited in place 12 April 2016 to point to
new work

   This version:
          http://www.w3.org/TR/2011/REC-CSS2-20110607

   Latest version:
          http://www.w3.org/TR/CSS2

   Previous versions:
          http://www.w3.org/TR/2011/PR-CSS2-20110412
          http://www.w3.org/TR/2008/REC-CSS2-20080411/

   Latest editor's draft:
          http://dev.w3.org/csswg/css2/

   Editors:
          Bert Bos <bert @w3.org>
          Tantek Çelik <tantek @cs.stanford.edu>
          Ian Hickson <ian @hixie.ch>
          Håkon Wium Lie <howcome @opera.com>

   Please refer to the errata for this document.

   This document is also available in these non-normative formats: plain
   text, gzip'ed tar file, zip file, gzip'ed PostScript, PDF. See also
   translations.

   Copyright © 2011 W3C^® (MIT, ERCIM, Keio), All Rights Reserved. W3C
   liability, trademark and document use rules apply.
     __________________________________________________________________

Abstract

   This specification defines Cascading Style Sheets, level 2 revision 1
   (CSS 2.1). CSS 2.1 is a style sheet language that allows authors and
   users to attach style (e.g., fonts and spacing) to structured documents
   (e.g., HTML documents and XML applications). By separating the
   presentation style of documents from the content of documents, CSS 2.1
   simplifies Web authoring and site maintenance.

   CSS 2.1 builds on CSS2 [CSS2] which builds on CSS1 [CSS1]. It supports
   media-specific style sheets so that authors may tailor the presentation
   of their documents to visual browsers, aural devices, printers, braille
   devices, handheld devices, etc. It also supports content positioning,
   table layout, features for internationalization and some properties
   related to user interface.

   CSS 2.1 corrects a few errors in CSS2 (the most important being a new
   definition of the height/width of absolutely positioned elements, more
   influence for HTML's "style" attribute and a new calculation of the
   'clip' property), and adds a few highly requested features which have
   already been widely implemented. But most of all CSS 2.1 represents a
   "snapshot" of CSS usage: it consists of all CSS features that are
   implemented interoperably at the date of publication of the
   Recommendation.

   CSS 2.1 is derived from and is intended to replace CSS2. Some parts of
   CSS2 are unchanged in CSS 2.1, some parts have been altered, and some
   parts removed. The removed portions may be used in a future CSS3
   specification. Future specs should refer to CSS 2.1 (unless they need
   features from CSS2 which have been dropped in CSS 2.1, and then they
   should only reference CSS2 for those features, or preferably reference
   such feature(s) in the respective CSS3 Module that includes those
   feature(s)).

Status of this document

   This section describes the status of this document at the time of its
   publication. Other documents may supersede this document. A list of
   current W3C publications and the latest revision of this technical
   report can be found in the W3C technical reports index at
   http://www.w3.org/TR/.

   This document has been reviewed by W3C Members, by software developers,
   and by other W3C groups and interested parties, and is endorsed by the
   Director as a W3C Recommendation. It is a stable document and may be
   used as reference material or cited from another document. W3C's role
   in making the Recommendation is to draw attention to the specification
   and to promote its widespread deployment. This enhances the
   functionality and interoperability of the Web.

   The (archived) public mailing list www-style@w3.org (see instructions)
   is preferred for discussion of this specification. When sending e-mail,
   please put the text “CSS21” in the subject, preferably like this:
   “[CSS21] …summary of comment…”

   This document was produced by the CSS Working Group (part of the Style
   Activity).

   This document was produced by a group operating under the 5 February
   2004 W3C Patent Policy. W3C maintains a public list of any patent
   disclosures made in connection with the deliverables of the group; that
   page also includes instructions for disclosing a patent. An individual
   who has actual knowledge of a patent which the individual believes
   contains Essential Claim(s) must disclose the information in accordance
   with section 6 of the W3C Patent Policy.

   The Working Group has created a test suite and an implementation
   report.

   All changes since the previous Working Draft, the previous Candidate
   Recommendation and the previous Recommendation are listed in
   appendix C.

   [ ] (hide)

   Note: Several sections of this specification have been updated by other
   specifications. Please, see "Cascading Style Sheets (CSS) — The
   Official Definition" in the latest CSS Snapshot for a list of
   specifications and the sections they replace.

   The CSS Working Group is also developing CSS level 2 revision 2
   (CSS 2.2).

Quick Table of Contents

     * 1 About the CSS 2.1 Specification
     * 2 Introduction to CSS 2.1
     * 3 Conformance: Requirements and Recommendations
     * 4 Syntax and basic data types
     * 5 Selectors
     * 6 Assigning property values, Cascading, and Inheritance
     * 7 Media types
     * 8 Box model
     * 9 Visual formatting model
     * 10 Visual formatting model details
     * 11 Visual effects
     * 12 Generated content, automatic numbering, and lists
     * 13 Paged media
     * 14 Colors and Backgrounds
     * 15 Fonts
     * 16 Text
     * 17 Tables
     * 18 User interface
     * Appendix A. Aural style sheets
     * Appendix B. Bibliography
     * Appendix C. Changes
     * Appendix D. Default style sheet for HTML 4
     * Appendix E. Elaborate description of Stacking Contexts
     * Appendix F. Full property table
     * Appendix G. Grammar of CSS 2.1
     * Appendix I. Index

Full Table of Contents

     * 1 About the CSS 2.1 Specification
          + 1.1 CSS 2.1 vs CSS 2
          + 1.2 Reading the specification
          + 1.3 How the specification is organized
          + 1.4 Conventions
               o 1.4.1 Document language elements and attributes
               o 1.4.2 CSS property definitions
                    # 1.4.2.1 Value
                    # 1.4.2.2 Initial
                    # 1.4.2.3 Applies to
                    # 1.4.2.4 Inherited
                    # 1.4.2.5 Percentage values
                    # 1.4.2.6 Media groups
                    # 1.4.2.7 Computed value
               o 1.4.3 Shorthand properties
               o 1.4.4 Notes and examples
               o 1.4.5 Images and long descriptions
          + 1.5 Acknowledgments
     * 2 Introduction to CSS 2.1
          + 2.1 A brief CSS 2.1 tutorial for HTML
          + 2.2 A brief CSS 2.1 tutorial for XML
          + 2.3 The CSS 2.1 processing model
               o 2.3.1 The canvas
               o 2.3.2 CSS 2.1 addressing model
          + 2.4 CSS design principles
     * 3 Conformance: Requirements and Recommendations
          + 3.1 Definitions
          + 3.2 UA Conformance
          + 3.3 Error conditions
          + 3.4 The text/css content type
     * 4 Syntax and basic data types
          + 4.1 Syntax
               o 4.1.1 Tokenization
               o 4.1.2 Keywords
                    # 4.1.2.1 Vendor-specific extensions
                    # 4.1.2.2 Informative Historical Notes
               o 4.1.3 Characters and case
               o 4.1.4 Statements
               o 4.1.5 At-rules
               o 4.1.6 Blocks
               o 4.1.7 Rule sets, declaration blocks, and selectors
               o 4.1.8 Declarations and properties
               o 4.1.9 Comments
          + 4.2 Rules for handling parsing errors
          + 4.3 Values
               o 4.3.1 Integers and real numbers
               o 4.3.2 Lengths
               o 4.3.3 Percentages
               o 4.3.4 URLs and URIs
               o 4.3.5 Counters
               o 4.3.6 Colors
               o 4.3.7 Strings
               o 4.3.8 Unsupported Values
          + 4.4 CSS style sheet representation
               o 4.4.1 Referring to characters not represented in a
                 character encoding
     * 5 Selectors
          + 5.1 Pattern matching
          + 5.2 Selector syntax
               o 5.2.1 Grouping
          + 5.3 Universal selector
          + 5.4 Type selectors
          + 5.5 Descendant selectors
          + 5.6 Child selectors
          + 5.7 Adjacent sibling selectors
          + 5.8 Attribute selectors
               o 5.8.1 Matching attributes and attribute values
               o 5.8.2 Default attribute values in DTDs
               o 5.8.3 Class selectors
          + 5.9 ID selectors
          + 5.10 Pseudo-elements and pseudo-classes
          + 5.11 Pseudo-classes
               o 5.11.1 :first-child pseudo-class
               o 5.11.2 The link pseudo-classes: :link and :visited
               o 5.11.3 The dynamic pseudo-classes: :hover, :active, and
                 :focus
               o 5.11.4 The language pseudo-class: :lang
          + 5.12 Pseudo-elements
               o 5.12.1 The :first-line pseudo-element
               o 5.12.2 The :first-letter pseudo-element
               o 5.12.3 The :before and :after pseudo-elements
     * 6 Assigning property values, Cascading, and Inheritance
          + 6.1 Specified, computed, and actual values
               o 6.1.1 Specified values
               o 6.1.2 Computed values
               o 6.1.3 Used values
               o 6.1.4 Actual values
          + 6.2 Inheritance
               o 6.2.1 The 'inherit' value
          + 6.3 The @import rule
          + 6.4 The cascade
               o 6.4.1 Cascading order
               o 6.4.2 !important rules
               o 6.4.3 Calculating a selector's specificity
               o 6.4.4 Precedence of non-CSS presentational hints
     * 7 Media types
          + 7.1 Introduction to media types
          + 7.2 Specifying media-dependent style sheets
               o 7.2.1 The @media rule
          + 7.3 Recognized media types
               o 7.3.1 Media groups
     * 8 Box model
          + 8.1 Box dimensions
          + 8.2 Example of margins, padding, and borders
          + 8.3 Margin properties: 'margin-top', 'margin-right',
            'margin-bottom', 'margin-left', and 'margin'
               o 8.3.1 Collapsing margins
          + 8.4 Padding properties: 'padding-top', 'padding-right',
            'padding-bottom', 'padding-left', and 'padding'
          + 8.5 Border properties
               o 8.5.1 Border width: 'border-top-width',
                 'border-right-width', 'border-bottom-width',
                 'border-left-width', and 'border-width'
               o 8.5.2 Border color: 'border-top-color',
                 'border-right-color', 'border-bottom-color',
                 'border-left-color', and 'border-color'
               o 8.5.3 Border style: 'border-top-style',
                 'border-right-style', 'border-bottom-style',
                 'border-left-style', and 'border-style'
               o 8.5.4 Border shorthand properties: 'border-top',
                 'border-right', 'border-bottom', 'border-left', and
                 'border'
          + 8.6 The box model for inline elements in bidirectional context
     * 9 Visual formatting model
          + 9.1 Introduction to the visual formatting model
               o 9.1.1 The viewport
               o 9.1.2 Containing blocks
          + 9.2 Controlling box generation
               o 9.2.1 Block-level elements and block boxes
                    # 9.2.1.1 Anonymous block boxes
               o 9.2.2 Inline-level elements and inline boxes
                    # 9.2.2.1 Anonymous inline boxes
               o 9.2.3 Run-in boxes
               o 9.2.4 The 'display' property
          + 9.3 Positioning schemes
               o 9.3.1 Choosing a positioning scheme: 'position' property
               o 9.3.2 Box offsets: 'top', 'right', 'bottom', 'left'
          + 9.4 Normal flow
               o 9.4.1 Block formatting contexts
               o 9.4.2 Inline formatting contexts
               o 9.4.3 Relative positioning
          + 9.5 Floats
               o 9.5.1 Positioning the float: the 'float' property
               o 9.5.2 Controlling flow next to floats: the 'clear'
                 property
          + 9.6 Absolute positioning
               o 9.6.1 Fixed positioning
          + 9.7 Relationships between 'display', 'position', and 'float'
          + 9.8 Comparison of normal flow, floats, and absolute
            positioning
               o 9.8.1 Normal flow
               o 9.8.2 Relative positioning
               o 9.8.3 Floating a box
               o 9.8.4 Absolute positioning
          + 9.9 Layered presentation
               o 9.9.1 Specifying the stack level: the 'z-index' property
          + 9.10 Text direction: the 'direction' and 'unicode-bidi'
            properties
     * 10 Visual formatting model details
          + 10.1 Definition of "containing block"
          + 10.2 Content width: the 'width' property
          + 10.3 Calculating widths and margins
               o 10.3.1 Inline, non-replaced elements
               o 10.3.2 Inline, replaced elements
               o 10.3.3 Block-level, non-replaced elements in normal flow
               o 10.3.4 Block-level, replaced elements in normal flow
               o 10.3.5 Floating, non-replaced elements
               o 10.3.6 Floating, replaced elements
               o 10.3.7 Absolutely positioned, non-replaced elements
               o 10.3.8 Absolutely positioned, replaced elements
               o 10.3.9 'Inline-block', non-replaced elements in normal
                 flow
               o 10.3.10 'Inline-block', replaced elements in normal flow
          + 10.4 Minimum and maximum widths: 'min-width' and 'max-width'
          + 10.5 Content height: the 'height' property
          + 10.6 Calculating heights and margins
               o 10.6.1 Inline, non-replaced elements
               o 10.6.2 Inline replaced elements, block-level replaced
                 elements in normal flow, 'inline-block' replaced elements
                 in normal flow and floating replaced elements
               o 10.6.3 Block-level non-replaced elements in normal flow
                 when 'overflow' computes to 'visible'
               o 10.6.4 Absolutely positioned, non-replaced elements
               o 10.6.5 Absolutely positioned, replaced elements
               o 10.6.6 Complicated cases
               o 10.6.7 'Auto' heights for block formatting context roots
          + 10.7 Minimum and maximum heights: 'min-height' and
            'max-height'
          + 10.8 Line height calculations: the 'line-height' and
            'vertical-align' properties
               o 10.8.1 Leading and half-leading
     * 11 Visual effects
          + 11.1 Overflow and clipping
               o 11.1.1 Overflow: the 'overflow' property
               o 11.1.2 Clipping: the 'clip' property
          + 11.2 Visibility: the 'visibility' property
     * 12 Generated content, automatic numbering, and lists
          + 12.1 The :before and :after pseudo-elements
          + 12.2 The 'content' property
          + 12.3 Quotation marks
               o 12.3.1 Specifying quotes with the 'quotes' property
               o 12.3.2 Inserting quotes with the 'content' property
          + 12.4 Automatic counters and numbering
               o 12.4.1 Nested counters and scope
               o 12.4.2 Counter styles
               o 12.4.3 Counters in elements with 'display: none'
          + 12.5 Lists
               o 12.5.1 Lists: the 'list-style-type', 'list-style-image',
                 'list-style-position', and 'list-style' properties
     * 13 Paged media
          + 13.1 Introduction to paged media
          + 13.2 Page boxes: the @page rule
               o 13.2.1 Page margins
               o 13.2.2 Page selectors: selecting left, right, and first
                 pages
               o 13.2.3 Content outside the page box
          + 13.3 Page breaks
               o 13.3.1 Page break properties: 'page-break-before',
                 'page-break-after', 'page-break-inside'
               o 13.3.2 Breaks inside elements: 'orphans', 'widows'
               o 13.3.3 Allowed page breaks
               o 13.3.4 Forced page breaks
               o 13.3.5 "Best" page breaks
          + 13.4 Cascading in the page context
     * 14 Colors and Backgrounds
          + 14.1 Foreground color: the 'color' property
          + 14.2 The background
               o 14.2.1 Background properties: 'background-color',
                 'background-image', 'background-repeat',
                 'background-attachment', 'background-position', and
                 'background'
     * 15 Fonts
          + 15.1 Introduction
          + 15.2 Font matching algorithm
          + 15.3 Font family: the 'font-family' property
               o 15.3.1 Generic font families
                    # 15.3.1.1 serif
                    # 15.3.1.2 sans-serif
                    # 15.3.1.3 cursive
                    # 15.3.1.4 fantasy
                    # 15.3.1.5 monospace
          + 15.4 Font styling: the 'font-style' property
          + 15.5 Small-caps: the 'font-variant' property
          + 15.6 Font boldness: the 'font-weight' property
          + 15.7 Font size: the 'font-size' property
          + 15.8 Shorthand font property: the 'font' property
     * 16 Text
          + 16.1 Indentation: the 'text-indent' property
          + 16.2 Alignment: the 'text-align' property
          + 16.3 Decoration
               o 16.3.1 Underlining, overlining, striking, and blinking:
                 the 'text-decoration' property
          + 16.4 Letter and word spacing: the 'letter-spacing' and
            'word-spacing' properties
          + 16.5 Capitalization: the 'text-transform' property
          + 16.6 White space: the 'white-space' property
               o 16.6.1 The 'white-space' processing model
               o 16.6.2 Example of bidirectionality with white space
                 collapsing
               o 16.6.3 Control and combining characters' details
     * 17 Tables
          + 17.1 Introduction to tables
          + 17.2 The CSS table model
               o 17.2.1 Anonymous table objects
          + 17.3 Columns
          + 17.4 Tables in the visual formatting model
               o 17.4.1 Caption position and alignment
          + 17.5 Visual layout of table contents
               o 17.5.1 Table layers and transparency
               o 17.5.2 Table width algorithms: the 'table-layout'
                 property
                    # 17.5.2.1 Fixed table layout
                    # 17.5.2.2 Automatic table layout
               o 17.5.3 Table height algorithms
               o 17.5.4 Horizontal alignment in a column
               o 17.5.5 Dynamic row and column effects
          + 17.6 Borders
               o 17.6.1 The separated borders model
                    # 17.6.1.1 Borders and Backgrounds around empty cells:
                      the 'empty-cells' property
               o 17.6.2 The collapsing border model
                    # 17.6.2.1 Border conflict resolution
               o 17.6.3 Border styles
     * 18 User interface
          + 18.1 Cursors: the 'cursor' property
          + 18.2 System Colors
          + 18.3 User preferences for fonts
          + 18.4 Dynamic outlines: the 'outline' property
               o 18.4.1 Outlines and the focus
          + 18.5 Magnification
     * Appendix A. Aural style sheets
          + A.1 The media types 'aural' and 'speech'
          + A.2 Introduction to aural style sheets
               o A.2.1 Angles
               o A.2.2 Times
               o A.2.3 Frequencies
          + A.3 Volume properties: 'volume'
          + A.4 Speaking properties: 'speak'
          + A.5 Pause properties: 'pause-before', 'pause-after', and
            'pause'
          + A.6 Cue properties: 'cue-before', 'cue-after', and 'cue'
          + A.7 Mixing properties: 'play-during'
          + A.8 Spatial properties: 'azimuth' and 'elevation'
          + A.9 Voice characteristic properties: 'speech-rate',
            'voice-family', 'pitch', 'pitch-range', 'stress', and
            'richness'
          + A.10 Speech properties: 'speak-punctuation' and
            'speak-numeral'
          + A.11 Audio rendering of tables
               o A.11.1 Speaking headers: the 'speak-header' property
          + A.12 Sample style sheet for HTML
          + A.13 Emacspeak
     * Appendix B. Bibliography
          + B.1 Normative references
          + B.2 Informative references
     * Appendix C. Changes
          + C.1 Additional property values
               o C.1.1 Section 4.3.6 Colors
               o C.1.2 Section 9.2.4 The 'display' property
               o C.1.3 Section 12.2 The 'content' property
               o C.1.4 Section 16.6 White space: the 'white-space'
                 property
               o C.1.5 Section 18.1 Cursors: the 'cursor' property
          + C.2 Changes
               o C.2.1 Section 1.1 CSS 2.1 vs CSS 2
               o C.2.2 Section 1.2 Reading the specification
               o C.2.3 Section 1.3 How the specification is organized
               o C.2.4 Section 1.4.2.1 Value
               o C.2.5 Section 1.4.2.6 Media groups
               o C.2.6 Section 1.4.2.7 Computed value
               o C.2.7 Section 1.4.4 Notes and examples
               o C.2.8 Section 1.5 Acknowledgments
               o C.2.9 Section 3.2 Conformance
               o C.2.10 Section 3.3 Error Conditions
               o C.2.11 Section 4.1.1 Tokenization
               o C.2.12 Section 4.1.3 Characters and case
               o C.2.13 Section 4.2 Rules for handling parsing errors
               o C.2.14 Section 4.3 Values
               o C.2.15 Section 4.3.2 Lengths
               o C.2.16 Section 4.3.4 URLs and URIs
               o C.2.17 Section 4.3.5 Counters
               o C.2.18 Section 4.3.6 Colors
               o C.2.19 Section 4.3.8 Unsupported Values
               o C.2.20 Section 4.4 CSS style sheet representation
               o C.2.21 Section 5.8.1 Matching attributes and attribute
                 values
               o C.2.22 Section 5.8.3 Class selectors
               o C.2.23 Section 5.9 ID selectors
               o C.2.24 Section 5.10 Pseudo-elements and pseudo-classes
               o C.2.25 Section 5.11.2 The link pseudo-classes: :link and
                 :visited
               o C.2.26 Section 5.11.4 The language pseudo-class: :lang
               o C.2.27 Section 5.12.1 The :first-line pseudo-element
               o C.2.28 Section 5.12.2 The :first-letter pseudo-element
               o C.2.29 Section 6.1 Specified, computed, and actual values
               o C.2.30 Section 6.4.1 Cascading order
               o C.2.31 Section 6.4.3 Calculating a selector's specificity
               o C.2.32 Section 6.4.4 Precedence of non-CSS presentational
                 hints
               o C.2.33 Section 7.3 Recognized Media Types
               o C.2.34 Section 7.3.1 Media Groups
               o C.2.35 Section 8.3 Margin properties
               o C.2.36 Section 8.3.1 Collapsing margins
               o C.2.37 Section 8.4 Padding properties
               o C.2.38 Section 8.5.2 Border color
               o C.2.39 Section 8.5.3 Border style
               o C.2.40 Section 8.6 The box model for inline elements in
                 bidirectional context
               o C.2.41 Section 9.1.2 Containing blocks
               o C.2.42 Section 9.2.1.1 Anonymous block boxes
               o C.2.43 Section 9.2.2.1 Anonymous inline boxes
               o C.2.44 Section 9.2.3 Run-in boxes
               o C.2.45 Section 9.2.4 The 'display' property
               o C.2.46 Section 9.3.1 Choosing a positioning scheme
               o C.2.47 Section 9.3.2 Box offsets
               o C.2.48 Section 9.4.1 Block formatting contexts
               o C.2.49 Section 9.4.2 Inline formatting context
               o C.2.50 Section 9.4.3 Relative positioning
               o C.2.51 Section 9.5 Floats
               o C.2.52 Section 9.5.1 Positioning the float
               o C.2.53 Section 9.5.2 Controlling flow next to floats
               o C.2.54 Section 9.7 Relationships between 'display',
                 'position', and 'float'
               o C.2.55 Section 9.9 Layered presentation
               o C.2.56 Section 9.10 Text direction
               o C.2.57 Chapter 10 Visual formatting model details
               o C.2.58 Section 10.1 Definition of "containing block"
               o C.2.59 Section 10.2 Content width
               o C.2.60 Section 10.3 Calculating widths and margins
               o C.2.61 Section 10.3.2 Inline, replaced elements
               o C.2.62 Section 10.3.3 Block-level, non-replaced elements
                 in normal flow
               o C.2.63 Section 10.3.4 Block-level, replaced elements in
                 normal flow
               o C.2.64 Section 10.3.5 Floating, non-replaced elements
               o C.2.65 Section 10.3.6 Floating, replaced elements
               o C.2.66 Section 10.3.7 Absolutely positioned, non-replaced
                 elements
               o C.2.67 Section 10.3.8 Absolutely positioned, replaced
                 elements
               o C.2.68 Section 10.4 Minimum and maximum widths
               o C.2.69 Section 10.5 Content height
               o C.2.70 Section 10.6 Calculating heights and margins
               o C.2.71 Section 10.6.1 Inline, non-replaced elements
               o C.2.72 Section 10.6.2 Inline replaced elements,
                 block-level replaced elements in normal flow,
                 'inline-block' replaced elements in normal flow and
                 floating replaced elements
               o C.2.73 Section 10.6.3 Block-level non-replaced elements
                 in normal flow when 'overflow' computes to 'visible'
               o C.2.74 Section 10.6.4 Absolutely positioned, non-replaced
                 elements
               o C.2.75 Section 10.6.5 Absolutely positioned, replaced
                 elements
               o C.2.76 Section 10.7 Minimum and maximum heights
               o C.2.77 Section 10.8 Line height calculations
               o C.2.78 Section 10.8.1 Leading and half-leading
               o C.2.79 Section 11.1 Overflow and clipping
               o C.2.80 Section 11.1.1 Overflow
               o C.2.81 Section 11.1.2 Clipping: the 'clip' property
               o C.2.82 Section 11.2 Visibility
               o C.2.83 Chapter 12 Generated content, automatic numbering,
                 and lists
               o C.2.84 Section 12.1 The :before and :after
                 pseudo-elements
               o C.2.85 Section 12.2 The 'content' property
               o C.2.86 Section 12.3.2 Inserting quotes with the 'content'
                 property
               o C.2.87 Section 12.4 Automatic counters and numbering
               o C.2.88 Section 12.4.1 Nested counters and scope
               o C.2.89 Section 12.5 Lists
               o C.2.90 Section 12.5.1 Lists
               o C.2.91 Chapter 13 Paged media
               o C.2.92 Section 13.2.2 Page selectors
               o C.2.93 Section 13.3.1 Page break properties
               o C.2.94 Section 13.3.3 Allowed page breaks
               o C.2.95 Section 14.2.1 Background properties
               o C.2.96 Section 14.3 Gamma correction
               o C.2.97 Chapter 15 Fonts
               o C.2.98 Section 15.2 Font matching algorithm
               o C.2.99 Section 15.2.2 Font family
               o C.2.100 Section 15.5 Small-caps
               o C.2.101 Section 15.6 Font boldness
               o C.2.102 Section 15.7 Font size
               o C.2.103 Chapter 16 Text
               o C.2.104 Section 16.2 Alignment
               o C.2.105 Section 16.3.1 Underlining, over lining,
                 striking, and blinking
               o C.2.106 Section 16.4 Letter and word spacing
               o C.2.107 Section 16.5 Capitalization
               o C.2.108 Section 16.6 White space
               o C.2.109 Chapter 17 Tables
               o C.2.110 Section 17.2 The CSS table model
               o C.2.111 Section 17.2.1 Anonymous table objects
               o C.2.112 Section 17.4 Tables in the visual formatting
                 model
               o C.2.113 Section 17.4.1 Caption position and alignment
               o C.2.114 Section 17.5 Visual layout of table contents
               o C.2.115 Section 17.5.1 Table layers and transparency
               o C.2.116 Section 17.5.2.1 Fixed table layout
               o C.2.117 Section 17.5.2.2 Automatic table layout
               o C.2.118 Section 17.5.3 Table height algorithms
               o C.2.119 Section 17.5.4 Horizontal alignment in a column
               o C.2.120 Section 17.6 Borders
               o C.2.121 Section 17.6.1 The separated borders model
               o C.2.122 Section 17.6.1.1 Borders and Backgrounds around
                 empty cells
               o C.2.123 Section 17.6.2 The collapsing border model
               o C.2.124 Section 17.6.2.1 Border conflict resolution
               o C.2.125 Section 18.1 Cursors: the 'cursor' property
               o C.2.126 Section 18.4 Dynamic outlines
               o C.2.127 Chapter 12 Generated content, automatic
                 numbering, and lists
               o C.2.128 Appendix A. Aural style sheets
               o C.2.129 Appendix A Section 5 Pause properties
               o C.2.130 Appendix A Section 6 Cue properties
               o C.2.131 Appendix A Section 7 Mixing properties
               o C.2.132 Appendix B Bibliography
               o C.2.133 Other
          + C.3 Errors
               o C.3.1 Shorthand properties
               o C.3.2 Applies to
               o C.3.3 Section 4.1.1 (and G2)
               o C.3.4 Section 4.1.3 Characters and case
               o C.3.5 Section 4.3 (Double sign problem)
               o C.3.6 Section 4.3.2 Lengths
               o C.3.7 Section 4.3.3 Percentages
               o C.3.8 Section 4.3.4 URLs and URIs
               o C.3.9 Section 4.3.5 Counters
               o C.3.10 Section 4.3.6 Colors
               o C.3.11 Section 4.3.7 Strings
               o C.3.12 Section 5.10 Pseudo-elements and pseudo-classes
               o C.3.13 Section 6.4 The cascade
               o C.3.14 Section 8.1 Box Dimensions
               o C.3.15 Section 8.2 Example of margins, padding, and
                 borders
               o C.3.16 Section 8.5.4 Border shorthand properties
               o C.3.17 Section 9.2.1 Block-level elements and block boxes
               o C.3.18 Section 9.3.1 Choosing a positioning scheme
               o C.3.19 Section 9.3.2 Box offsets
               o C.3.20 Section 9.4.1 Block formatting contexts
               o C.3.21 Section 9.4.2 Inline formatting context
               o C.3.22 Section 9.4.3 Relative positioning
               o C.3.23 Section 9.5 Floats
               o C.3.24 Section 9.5.1 Positioning the float
               o C.3.25 Section 9.5.2 Controlling flow next to floats
               o C.3.26 Section 9.6 Absolute positioning
               o C.3.27 Section 9.7 Relationships between 'display',
                 'position', and 'float'
               o C.3.28 Section 9.10 Text direction
               o C.3.29 Section 10.1 Definition of "containing block"
               o C.3.30 Section 10.3.3 Block-level, non-replaced elements
                 in normal flow
               o C.3.31 Section 10.4 Minimum and maximum widths
               o C.3.32 Section 10.6.3 Block-level non-replaced elements
                 in normal flow when 'overflow' computes to 'visible'
               o C.3.33 Section 10.7 Minimum and maximum heights
               o C.3.34 Section 11.1.1 Overflow
               o C.3.35 Section 11.1.2 Clipping: the 'clip' property
               o C.3.36 Section 11.2 Visibility
               o C.3.37 Section 12.4.2 Counter styles
               o C.3.38 Section 12.6.2 Lists
               o C.3.39 Section 14.2 The background
               o C.3.40 Section 14.2.1 Background properties
               o C.3.41 Section 15.2 Font matching algorithm
               o C.3.42 Section 15.7 Font size
               o C.3.43 Section 16.1 Indentation
               o C.3.44 Section 16.2 Alignment
               o C.3.45 Section 17.2 The CSS table model
               o C.3.46 Section 17.2.1 Anonymous table objects
               o C.3.47 Section 17.4 Tables in the visual formatting model
               o C.3.48 Section 17.5 Visual layout of table contents
               o C.3.49 Section 17.5.1 Table layers and transparency
               o C.3.50 Section 17.6.1 The separated borders model
               o C.3.51 Section 18.2 System Colors
               o C.3.52 Section E.2 Painting order
          + C.4 Clarifications
               o C.4.1 Section 2.1 A brief CSS 2.1 tutorial for HTML
               o C.4.2 Section 2.2 A brief CSS 2.1 tutorial for XML
               o C.4.3 Section 2.3 The CSS 2.1 processing model
               o C.4.4 Section 3.1 Definitions
               o C.4.5 Section 4.1 Syntax
               o C.4.6 Section 4.1.1 Tokenization
               o C.4.7 Section 4.1.3 Characters and case
               o C.4.8 Section 4.1.7 Rule sets, declaration blocks, and
                 selectors
               o C.4.9 Section 4.2 Rules for handling parsing errors
               o C.4.10 Section 4.3.1 Integers and real numbers
               o C.4.11 Section 4.3.2 Lengths
               o C.4.12 Section 4.3.4 URLs and URIs
               o C.4.13 Section 5.1 Pattern matching
               o C.4.14 Section 5.7 Adjacent sibling selectors
               o C.4.15 Section 5.8.1 Matching attributes and attribute
                 values
               o C.4.16 Section 5.8.2 Default attribute values in DTDs
               o C.4.17 Section 5.9 ID selectors
               o C.4.18 Section 5.11.3 The dynamic pseudo-classes: :hover,
                 :active, and :focus
               o C.4.19 Section 5.11.4 The language pseudo-class: :lang
               o C.4.20 Section 5.12.2 The :first-letter pseudo-element
               o C.4.21 Section 6.2 Inheritance
               o C.4.22 Section 6.2.1 The 'inherit' value
               o C.4.23 Section 6.3 The @import rule
               o C.4.24 Section 6.4 The Cascade
               o C.4.25 Section 6.4.1 Cascading order
               o C.4.26 Section 6.4.3 Calculating a selector's specificity
               o C.4.27 Section 7.2.1 The @media rule
               o C.4.28 Section 7.3 Recognized media types
               o C.4.29 Section 7.3.1 Media groups
               o C.4.30 Section 8.1 Box dimensions
               o C.4.31 Section 8.3 Margin properties
               o C.4.32 Section 8.3.1 Collapsing margins
               o C.4.33 Section 8.5.3 Border style
               o C.4.34 Section 9.1.1 The viewport
               o C.4.35 Section 9.2.4 The 'display' property
               o C.4.36 Section 9.3.1 Choosing a positioning scheme
               o C.4.37 Section 9.3.2 Box offsets
               o C.4.38 Section 9.4.2 Inline formatting context
               o C.4.39 Section 9.4.3 Relative positioning
               o C.4.40 Section 9.5 Floats
               o C.4.41 Section 9.5.1 Positioning the float
               o C.4.42 Section 9.5.2 Controlling flow next to floats
               o C.4.43 Section 9.8 Comparison of normal flow, floats, and
                 absolute positioning
               o C.4.44 Section 10.1 Definition of "containing block"
               o C.4.45 Section 10.2 Content width
               o C.4.46 Section 10.3.3 Block-level, non-replaced elements
                 in normal flow
               o C.4.47 Section 10.3.8 Absolutely positioning, replaced
                 elements
               o C.4.48 Section 10.4 Minimum and maximum widths
               o C.4.49 Section 10.6 Calculating heights and margins
               o C.4.50 Section 10.7 Minimum and maximum heights
               o C.4.51 Section 10.8 Line height calculations
               o C.4.52 Section 10.8.1 Leading and half-leading
               o C.4.53 Section 11.1 Overflow and clipping
               o C.4.54 Section 11.1.1 Overflow
               o C.4.55 Section 11.1.2 Clipping
               o C.4.56 Section 11.2 Visibility
               o C.4.57 Section 12.1 The :before and :after
                 pseudo-elements
               o C.4.58 Section 12.2 The 'content' property
               o C.4.59 Section 12.3.2 Inserting quotes with the 'content'
                 property
               o C.4.60 Section 12.4 Automatic counters and numbering
               o C.4.61 Section 12.4.3 Counters in elements with 'display:
                 none'
               o C.4.62 Section 14.2 The background
               o C.4.63 Section 15.1 Fonts Introduction
               o C.4.64 Section 15.2 Font matching algorithm
               o C.4.65 Section 15.2.2 Font family
               o C.4.66 Section 15.3.1 Generic font families
               o C.4.67 Section 15.4 Font styling
               o C.4.68 Section 15.5 Small-caps
               o C.4.69 Section 15.6 Font boldness
               o C.4.70 Section 15.7 Font size
               o C.4.71 Section 16.1 Indentation
               o C.4.72 Section 16.2 Alignment
               o C.4.73 Section 16.3.1 Underlining, over lining, striking,
                 and blinking
               o C.4.74 Section 16.5 Capitalization
               o C.4.75 Section 16.6 White space
               o C.4.76 Section 17.1 Introduction to tables
               o C.4.77 Section 17.2 The CSS table model
               o C.4.78 Section 17.2.1 Anonymous table objects
               o C.4.79 Section 17.4 Tables in the visual formatting model
               o C.4.80 Section 17.5 Visual layout of table contents
               o C.4.81 Section 17.5.1 Table layers and transparency
               o C.4.82 Section 17.5.2 Table width algorithms
               o C.4.83 Section 17.5.2.1 Fixed table layout
               o C.4.84 Section 17.5.2.2 Automatic table layout
               o C.4.85 Section 17.5.4 Horizontal alignment in a column
               o C.4.86 Section 17.5.5 Dynamic row and column effects
               o C.4.87 Section 17.6.1 The separated borders model
               o C.4.88 Section 17.6.2 The collapsing borders model
               o C.4.89 Section 18.2 System Colors
               o C.4.90 Section 18.4 Dynamic outlines
               o C.4.91 Section 18.4.1 Outlines and the focus
               o C.4.92 Appendix D Default style sheet for HTML 4
          + C.5 Errata since the Candidate Recommendation of July 2007
               o C.5.1 Section 1.4.2.1 Value
               o C.5.2 Section 2.3 The CSS 2.1 processing model
               o C.5.3 Section 3.1 Definitions
               o C.5.4 Section 4.1.1 Tokenization
               o C.5.5 Section 4.1.2.2 Informative Historical Notes
               o C.5.6 Section 4.1.3 Characters and case
               o C.5.7 Section 4.1.3 Characters and case
               o C.5.8 Section 4.1.3 Characters and case
               o C.5.9 Section 4.1.3 Characters and case
               o C.5.10 Section 4.1.5 At-rules
               o C.5.11 Section 4.1.7 Rule sets, declaration blocks, and
                 selectors
               o C.5.12 Section 4.2 Rules for handling parsing errors
               o C.5.13 Section 4.2 Rules for handling parsing errors
               o C.5.14 Section 4.3.2 Lengths
               o C.5.15 Section 4.3.5 Counters
               o C.5.16 Section 5.8.1 Matching attributes and attribute
                 values
               o C.5.17 Section 5.8.2 Default attribute values in DTDs
               o C.5.18 Section 5.11.4 The language pseudo-class: :lang
               o C.5.19 Section 5.12.3 The :before and :after
                 pseudo-elements
               o C.5.20 Section 6.3 The @import rule
               o C.5.21 Section 6.3 The @import rule
               o C.5.22 Section 6.4.1 Cascading order
               o C.5.23 Section 6.4.1 Cascading order
               o C.5.24 Section 7.2.1 The @media rule
               o C.5.25 Section 8.3.1 Collapsing margins
               o C.5.26 Section 8.3.1 Collapsing margins
               o C.5.27 Section 8.3.1 Collapsing margins
               o C.5.28 Section 9.2.2 Inline-level elements and inline
                 boxes
               o C.5.29 Section 9.2.4 The 'display' property
               o C.5.30 Section 9.3.2 Box offsets: 'top', 'right',
                 'bottom', 'left'
               o C.5.31 Section 9.5 Floats
               o C.5.32 Section 9.5 Floats
               o C.5.33 Section 9.5.2 Controlling flow next to floats: the
                 'clear' property
               o C.5.34 Section 9.6.1 Fixed positioning
               o C.5.35 Section 9.9.1 Specifying the stack level: the
                 'z-index' property
               o C.5.36 Section 10.1 Definition of "containing block"
               o C.5.37 Section 10.3 Calculating widths and margins
               o C.5.38 Section 10.3.1 Inline, non-replaced elements
               o C.5.39 Section 10.3.2 Inline, replaced elements
               o C.5.40 Section 10.3.2 Inline, replaced elements
               o C.5.41 Section 10.3.3 Block-level, non-replaced elements
                 in normal flow
               o C.5.42 Section 10.3.7 Absolutely positioned, non-replaced
                 elements
               o C.5.43 Section 10.3.7 Absolutely positioned, non-replaced
                 elements
               o C.5.44 Section 10.3.8 Absolutely positioned, replaced
                 elements
               o C.5.45 Section 10.3.8 Absolutely positioned, replaced
                 elements
               o C.5.46 Section 10.3.8 Absolutely positioned, replaced
                 elements
               o C.5.47 Section 10.5 Content height: the 'height' property
               o C.5.48 Section 10.6.2 Inline replaced elements […]
               o C.5.49 Section 10.6.4 Absolutely positioned, non-replaced
                 elements
               o C.5.50 Section 10.6.5 Absolutely positioned, replaced
                 elements
               o C.5.51 Section 10.8.1 Leading and half-leading
               o C.5.52 Section 11.1.1 Overflow: the 'overflow' property
               o C.5.53 Section 11.1.2 Clipping: the 'clip' property
               o C.5.54 Section 12.2 The 'content' property
               o C.5.55 Section 12.4.2 Counter styles
               o C.5.56 Section 12.5 Lists
               o C.5.57 Section 12.5.1 Lists: the 'list-style-type',
                 'list-style-image', 'list-style-position', and
                 'list-style' properties
               o C.5.58 Section 12.5.1 Lists: the 'list-style-type',
                 'list-style-image', 'list-style-position', and
                 'list-style' properties
               o C.5.59 Section 12.5.1 Lists: the 'list-style-type',
                 'list-style-image', 'list-style-position', and
                 'list-style' properties
               o C.5.60 Section 13.2 Page boxes: the @page rule
               o C.5.61 Section 13.2.1.1 Rendering page boxes that do not
                 fit a target sheet
               o C.5.62 Section 13.2.3 Content outside the page box
               o C.5.63 Section 13.3.1 Page break properties:
                 'page-break-before', 'page-break-after',
                 'page-break-inside'
               o C.5.64 Section 13.3.1 Page break properties:
                 'page-break-before', 'page-break-after',
                 'page-break-inside'
               o C.5.65 Section 13.3.2 Breaks inside elements: 'orphans',
                 'widows'
               o C.5.66 Section 13.3.2 Breaks inside elements: 'orphans',
                 'widows'
               o C.5.67 Section 13.3.3 Allowed page breaks
               o C.5.68 Section 13.3.3 Allowed page breaks
               o C.5.69 Section 13.3.3 Allowed page breaks
               o C.5.70 Section 13.3.5 "Best" page breaks
               o C.5.71 Section 14.2 The background
               o C.5.72 Section 14.2 The background
               o C.5.73 Section 14.2.1 Background properties:
                 'background-color', 'background-image',
                 'background-repeat', 'background-attachment',
                 'background-position', and 'background'
               o C.5.74 Section 15.6 Font boldness: the 'font-weight'
                 property
               o C.5.75 Section 16.6 Whitespace: the 'white-space'
                 property
               o C.5.76 Section 16.6.1 The 'white-space' processing model
               o C.5.77 Section 17.2.1 Anonymous table objects
               o C.5.78 Section 17.2.1 Anonymous table objects
               o C.5.79 Section 17.4 Tables in the visual formatting model
               o C.5.80 Section 17.5.4 Horizontal alignment in a column
               o C.5.81 Section 18.1 Cursors: the 'cursor' property
               o C.5.82 Section B.2 Informative references
               o C.5.83 Appendix D. Default style sheet for HTML 4
               o C.5.84 Appendix D. Default style sheet for HTML 4
               o C.5.85 Section E.2 Painting order
               o C.5.86 Appendix G. Grammar of CSS 2.1
               o C.5.87 Section G.1 Grammar
               o C.5.88 Section G.2 Lexical scanner
               o C.5.89 Section G.2 Lexical scanner
               o C.5.90 Section G.2 Lexical scanner
               o C.5.91 Section G.2 Lexical scanner
               o C.5.92 Appendix I. Index
          + C.6 Errata since the Candidate Recommendation of April 2009
               o C.6.1 Section 4.2 Rules for handling parsing errors
               o C.6.2 Section 13.3.3 Allowed page breaks
               o C.6.3 Section 15.3 Font family: the 'font-family'
                 property
               o C.6.4 Section 15.3.1.1 serif
               o C.6.5 Section 15.7 Font size: the 'font-size' property
               o C.6.6 Section 17.5.2.1 Fixed table layout
               o C.6.7 Section 17.5.3 Table height layout
               o C.6.8 Appendix G. Grammar of CSS 2.1
          + C.7 Errata since the Candidate Recommendation of September
            2009
               o C.7.1 Section 1.4.2.1 Value
               o C.7.2 Section 3.1 Definitions
               o C.7.3 Section 4.1.1 Tokenization
               o C.7.4 Section 4.1.1 Tokenization
               o C.7.5 Section 4.1.1 Tokenization
               o C.7.6 Section 4.1.1 Tokenization
               o C.7.7 Section 4.1.2.2 Informative Historical Notes
               o C.7.8 Section 4.1.3 Characters and case
               o C.7.9 Section 4.1.3 Characters and case
               o C.7.10 Section 4.1.8 Declarations and properties
               o C.7.11 Section 4.2 Rules for handling parsing errors
               o C.7.12 Section 4.3.2 Lengths
               o C.7.13 Section 4.3.2 Lengths
               o C.7.14 Section 4.3.4 URLs and URIs
               o C.7.15 Section 4.3.4 URLs and URIs
               o C.7.16 Section 5.8.2 Default attribute values in DTDs
               o C.7.17 Section 5.11.4 The language pseudo-class: :lang
               o C.7.18 Section 5.12 Pseudo-elements
               o C.7.19 Section 5.12.1 The :first-line pseudo-element
               o C.7.20 Section 5.12.2 The :first-letter pseudo-element
               o C.7.21 Section 6.2 Inheritance
               o C.7.22 Section 6.4.4 Precedence of non-CSS presentational
                 hints
               o C.7.23 Section 7.3 Recognized media types
               o C.7.24 Section 8.3.1 Collapsing margins
               o C.7.25 Section 8.3.1 Collapsing margins
               o C.7.26 Section 9.2.1 Block-level elements and block boxes
               o C.7.27 Section 9.2.1.1 Anonymous block boxes
               o C.7.28 Section 9.2.1.1 Anonymous block boxes
               o C.7.29 Section 9.2.1.1 Anonymous block boxes
               o C.7.30 Section 9.2.1.1 Anonymous block boxes
               o C.7.31 Section 9.2.2 Inline-level elements and inline
                 boxes
               o C.7.32 Section 9.2.3 Run-in boxes
               o C.7.33 Section 9.2.4 The 'display' property
               o C.7.34 Section 9.2.4 The 'display' property
               o C.7.35 Section 9.3 Positioning schemes
               o C.7.36 Section 9.4 Normal flow
               o C.7.37 Section 9.3.2 Box offsets: 'top', 'right',
                 'bottom', 'left'
               o C.7.38 Section 9.5 Floats
               o C.7.39 Section 9.5 Floats
               o C.7.40 Section 9.5.2 Controlling flow next to floats: the
                 'clear' property
               o C.7.41 Section 9.5.2 Controlling flow next to floats: the
                 'clear' property
               o C.7.42 Section 9.5.2 Controlling flow next to floats: the
                 'clear' property
               o C.7.43 Section 9.5.2 Controlling flow next to floats: the
                 'clear' property
               o C.7.44 Section 14.2.1 Background properties
               o C.7.45 Section 9.9.1 Specifying the stack level: the
                 'z-index' property
               o C.7.46 Section 9.10 Text direction: the 'direction' and
                 'unicode-bidi' properties
               o C.7.47 Section 9.10 Text direction: the 'direction' and
                 'unicode-bidi' properties
               o C.7.48 Section 9.10 Text direction: the 'direction' and
                 'unicode-bidi' properties
               o C.7.49 Section 10.1 Definition of "containing block"
               o C.7.50 Section 10.2 Content width: the 'width' property
               o C.7.51 Section 10.2 Content width: the 'width' property
               o C.7.52 Section 10.2 Content width: the 'width' property
               o C.7.53 Section 10.5 Content height: the 'height' property
               o C.7.54 Section 10.5 Content height: the 'height' property
               o C.7.55 Section 10.6.7 'Auto' heights for block formatting
                 context roots
               o C.7.56 Section 10.7 Minimum and maximum heights:
                 'min-height' and 'max-height'
               o C.7.57 Section 10.8 Line height calculations: the
                 'line-height' and 'vertical-align' properties
               o C.7.58 Section 10.8 Line height calculations: the
                 'line-height' and 'vertical-align' properties
               o C.7.59 Section 10.8.1 Leading and half-leading
               o C.7.60 Section 10.8.1 Leading and half-leading
               o C.7.61 Section 10.8.1 Leading and half-leading
               o C.7.62 Section 11.1 Overflow and clipping
               o C.7.63 Section 11.1.1 Overflow: the 'overflow' property
               o C.7.64 Section 11.1.1 Overflow: the 'overflow' property
               o C.7.65 Section 11.1.1 Overflow: the 'overflow' property
               o C.7.66 Section 11.1.2 Clipping: the 'clip' property
               o C.7.67 Section 12.5 Lists
               o C.7.68 Section 12.5.1 Lists: the 'list-style-type',
                 'list-style-image', 'list-style-position', and
                 'list-style' properties
               o C.7.69 Section 12.5.1 Lists: the 'list-style-type',
                 'list-style-image', 'list-style-position', and
                 'list-style' properties
               o C.7.70 Section 12.5.1 Lists: the 'list-style-type',
                 'list-style-image', 'list-style-position', and
                 'list-style' properties
               o C.7.71 Section 12.5.1 Lists: the 'list-style-type',
                 'list-style-image', 'list-style-position', and
                 'list-style' properties
               o C.7.72 Section 12.5.1 Lists: the 'list-style-type',
                 'list-style-image', 'list-style-position', and
                 'list-style' properties
               o C.7.73 Section 13.2 Page boxes: the @page rule
               o C.7.74 Section 13.2.2 Page selectors: selecting left,
                 right, and first pages
               o C.7.75 Section 13.3.2 Breaks inside elements: 'orphans',
                 'widows'
               o C.7.76 Section 13.3.3 Allowed page breaks
               o C.7.77 Section 15.3 Font family: the 'font-family'
                 property
               o C.7.78 Section 15.3.1 Generic font families
               o C.7.79 Section 15.6 Font boldness: the 'font-weight'
                 property
               o C.7.80 Section 15.6 Font boldness: the 'font-weight'
                 property
               o C.7.81 Section 15.7 Font size: the 'font-size' property
               o C.7.82 Section 16.1 Indentation: the 'text-indent'
                 property
               o C.7.83 Section 16.1 Indentation: the 'text-indent'
                 property
               o C.7.84 Section 16.2 Alignment: the 'text-align' property
               o C.7.85 Section 16.2 Alignment: the 'text-align' property
               o C.7.86 Section 16.3.1 Underlining, overlining, striking,
                 and blinking: the 'text-decoration' property
               o C.7.87 Section 16.3.1 Underlining, overlining, striking,
                 and blinking: the 'text-decoration' property
               o C.7.88 Section 16.4 Letter and word spacing: the
                 'letter-spacing' and 'word-spacing' properties
               o C.7.89 Section 16.6 White space: the 'white-space'
                 property
               o C.7.90 Section 16.6.1 The 'white-space' processing model
               o C.7.91 Section 16.6.1 The 'white-space' processing model
               o C.7.92 Section 16.6.1 The 'white-space' processing model
               o C.7.93 Section 17.2 The CSS table model
               o C.7.94 Section 17.2.1 Anonymous table objects
               o C.7.95 Section 17.2.1 Anonymous table objects
               o C.7.96 Section 17.4 Tables in the visual formatting model
               o C.7.97 Section 17.4 Tables in the visual formatting model
               o C.7.98 Section 17.5.2.2 Automatic table layout
               o C.7.99 Section 17.5.3 Table height algorithms
               o C.7.100 Section 17.5.4 Horizontal alignment in a column
               o C.7.101 Section B.2 Informative references
               o C.7.102 Section D. Default style sheet for HTML 4
               o C.7.103 Section E.2 Painting order
               o C.7.104 Appendix G Grammar of CSS 2.1
          + C.8 Changes since the working draft of 7 December 2010
               o C.8.1 8.3.1 Collapsing margins
               o C.8.2 10.8.1 Leading and half-leading
               o C.8.3 10.3 Calculating widths and margins
               o C.8.4 14.3 Gamma correction
               o C.8.5 11.1.2 Clipping: the 'clip' property
               o C.8.6 9.4.2 Inline formatting contexts
               o C.8.7 10.3.2 Inline, replaced elements
               o C.8.8 10.1 Definition of "containing block"
               o C.8.9 13.2.2 Page selectors: selecting left, right, and
                 first pages
               o C.8.10 8.3.1 Collapsing margins
               o C.8.11 10.8 Line height calculations: the 'line-height'
                 and 'vertical-align' properties
               o C.8.12 10.8.1 Leading and half-leading
               o C.8.13 10.6.1 Inline, non-replaced elements
               o C.8.14 9.5.1 Positioning the float: the 'float' property
               o C.8.15 9.2.1.1 Anonymous block boxes
               o C.8.16 5.12.1 The :first-line pseudo-element
               o C.8.17 16.6 White space: the 'white-space' property
               o C.8.18 12.5.1 Lists: the 'list-style-type',
                 'list-style-image', 'list-style-position', and
                 'list-style' properties
               o C.8.19 9.7 Relationships between 'display', 'position',
                 and 'float'
               o C.8.20 9.4.2 Inline formatting contexts
               o C.8.21 4.1.9 Comments
               o C.8.22 12.5.1 Lists: the 'list-style-type',
                 'list-style-image', 'list-style-position', and
                 'list-style' properties
               o C.8.23 9.5.1 Positioning the float: the 'float' property
               o C.8.24 9.3 Positioning schemes
               o C.8.25 9.10 Text direction: the 'direction' and
                 'unicode-bidi' properties
               o C.8.26 16.3.1 Underlining, overlining, striking, and
                 blinking: the 'text-decoration' property
               o C.8.27 16.3.1 Underlining, overlining, striking, and
                 blinking: the 'text-decoration' property
               o C.8.28 10.4 Minimum and maximum widths: 'min-width' and
                 'max-width'
               o C.8.29 9.3.2 Box offsets: 'top', 'right', 'bottom',
                 'left'
               o C.8.30 9.2.1.1 Anonymous block boxes
               o C.8.31 17.4 Tables in the visual formatting model
               o C.8.32 11.1.2 Clipping: the 'clip' property
               o C.8.33 13.2 Page boxes: the @page rule
               o C.8.34 4.1.1 Tokenization
               o C.8.35 4.2 Rules for handling parsing errors
               o C.8.36 3.1 Definitions
               o C.8.37 4.3.4 URLs and URIs
               o C.8.38 9.5 Floats
               o C.8.39 11.1.1 Overflow: the 'overflow' property
               o C.8.40 9.2.1.1 Anonymous block boxes
               o C.8.41 16.2 Alignment: the 'text-align' property
               o C.8.42 9.5 Floats
               o C.8.43 9.4.2 Inline formatting contexts
               o C.8.44 5.12 Pseudo-elements
               o C.8.45 9.5 Floats
               o C.8.46 9.5 Floats
               o C.8.47 14.2.1 Background properties: 'background-color',
                 'background-image', 'background-repeat',
                 'background-attachment', 'background-position', and
                 'background'
               o C.8.48 9.2.4 The 'display' property
               o C.8.49 6.1.2 Computed values
               o C.8.50 10.3.2 Inline, replaced elements
               o C.8.51 Section 9.5.2 Controlling flow next to floats: the
                 'clear' property
               o C.8.52 G.2 Lexical scanner
               o C.8.53 Section 9.5.2 Controlling flow next to floats: the
                 'clear' property
               o C.8.54 9.5 Floats
               o C.8.55 10.6.3 Block-level non-replaced elements in normal
                 flow when 'overflow' computes to 'visible'
     * Appendix D. Default style sheet for HTML 4
     * Appendix E. Elaborate description of Stacking Contexts
          + E.1 Definitions
          + E.2 Painting order
          + E.3 Notes
     * Appendix F. Full property table
     * Appendix G. Grammar of CSS 2.1
          + G.1 Grammar
          + G.2 Lexical scanner
          + G.3 Comparison of tokenization in CSS 2.1 and CSS1
          + G.4 Implementation note
     * Appendix I. Index

                       1 About the CSS 2.1 Specification

   Contents
     * 1.1 CSS 2.1 vs CSS 2
     * 1.2 Reading the specification
     * 1.3 How the specification is organized
     * 1.4 Conventions
          + 1.4.1 Document language elements and attributes
          + 1.4.2 CSS property definitions
               o 1.4.2.1 Value
               o 1.4.2.2 Initial
               o 1.4.2.3 Applies to
               o 1.4.2.4 Inherited
               o 1.4.2.5 Percentage values
               o 1.4.2.6 Media groups
               o 1.4.2.7 Computed value
          + 1.4.3 Shorthand properties
          + 1.4.4 Notes and examples
          + 1.4.5 Images and long descriptions
     * 1.5 Acknowledgments

1.1 CSS 2.1 vs CSS 2

   The CSS community has gained significant experience with the CSS2
   specification since it became a recommendation in 1998. Errors in the
   CSS2 specification have subsequently been corrected via the publication
   of various errata, but there has not yet been an opportunity for the
   specification to be changed based on experience gained.

   While many of these issues will be addressed by the upcoming CSS3
   specifications, the current state of affairs hinders the implementation
   and interoperability of CSS2. The CSS 2.1 specification attempts to
   address this situation by:
     * Maintaining compatibility with those portions of CSS2 that are
       widely accepted and implemented.
     * Incorporating all published CSS2 errata.
     * Where implementations overwhelmingly differ from the CSS2
       specification, modifying the specification to be in accordance with
       generally accepted practice.
     * Removing CSS2 features which, by virtue of not having been
       implemented, have been rejected by the CSS community. CSS 2.1 aims
       to reflect what CSS features are reasonably widely implemented for
       HTML and XML languages in general (rather than only for a
       particular XML language, or only for HTML).
     * Removing CSS2 features that will be obsoleted by CSS3, thus
       encouraging adoption of the proposed CSS3 features in their place.
     * Adding a (very) small number of new property values, when
       implementation experience has shown that they are needed for
       implementing CSS2.

   Thus, while it is not the case that a CSS2 style sheet is necessarily
   forwards-compatible with CSS 2.1, it is the case that a style sheet
   restricting itself to CSS 2.1 features is more likely to find a
   compliant user agent today and to preserve forwards compatibility in
   the future. While breaking forward compatibility is not desirable, we
   believe the advantages to the revisions in CSS 2.1 are worthwhile.

   CSS 2.1 is derived from and is intended to replace CSS2. Some parts of
   CSS2 are unchanged in CSS 2.1, some parts have been altered, and some
   parts removed. The removed portions may be used in a future CSS3
   specification. Future specs should refer to CSS 2.1 (unless they need
   features from CSS2 which have been dropped in CSS 2.1, and then they
   should only reference CSS2 for those features, or preferably reference
   such feature(s) in the respective CSS3 Module that includes those
   feature(s)).

1.2 Reading the specification

   This section is non-normative.

   This specification has been written with two types of readers in mind:
   CSS authors and CSS implementors. We hope the specification will
   provide authors with the tools they need to write efficient,
   attractive, and accessible documents, without overexposing them to
   CSS's implementation details. Implementors, however, should find all
   they need to build conforming user agents. The specification begins
   with a general presentation of CSS and becomes more and more technical
   and specific towards the end. For quick access to information, a
   general table of contents, specific tables of contents at the beginning
   of each section, and an index provide easy navigation, in both the
   electronic and printed versions.

   The specification has been written with two modes of presentation in
   mind: electronic and printed. Although the two presentations will no
   doubt be similar, readers will find some differences. For example,
   links will not work in the printed version (obviously), and page
   numbers will not appear in the electronic version. In case of a
   discrepancy, the electronic version is considered the authoritative
   version of the document.

1.3 How the specification is organized

   This section is non-normative.

   The specification is organized into the following sections:

   Section 2: An introduction to CSS 2.1
          The introduction includes a brief tutorial on CSS 2.1 and a
          discussion of design principles behind CSS 2.1.

   Sections 3 - 18: CSS 2.1 reference manual.
          The bulk of the reference manual consists of the CSS 2.1
          language reference. This reference defines what may go into a
          CSS 2.1 style sheet (syntax, properties, property values) and
          how user agents must interpret these style sheets in order to
          claim conformance.

   Appendixes:
          Appendixes contain information about aural properties
          (non-normative), a sample style sheet for HTML 4, changes from
          CSS2, the grammar of CSS 2.1, a list of normative and
          informative references, and two indexes: one for properties and
          one general index.

1.4 Conventions

  1.4.1 Document language elements and attributes

     * CSS property and pseudo-class names are delimited by single quotes.
     * CSS values are delimited by single quotes.
     * Document language attribute names are in lowercase letters and
       delimited by double quotes.

  1.4.2 CSS property definitions

   Each CSS property definition begins with a summary of key information
   that resembles the following:

   'property-name'

          Value:            legal values & syntax
          Initial:          initial value
          Applies to:       elements this property applies to
          Inherited:        whether the property is inherited
          Percentages:      how percentage values are interpreted
          Media:            which media groups the property applies to
          Computed value:   how to compute the computed value

    1.4.2.1 Value

   This part specifies the set of valid values for the property whose name
   is 'property-name'. A property value can have one or more components.
   Component value types are designated in several ways:
    1. keyword values (e.g., auto, disc, etc.)
    2. basic data types, which appear between "<" and ">" (e.g., <length>,
       <percentage>, etc.). In the electronic version of the document,
       each instance of a basic data type links to its definition.
    3. types that have the same range of values as a property bearing the
       same name (e.g., <'border-width'> <'background-attachment'>, etc.).
       In this case, the type name is the property name (complete with
       quotes) between "<" and ">" (e.g., <'border-width'>). Such a type
       does not include the value 'inherit'. In the electronic version of
       the document, each instance of this type of non-terminal links to
       the corresponding property definition.
    4. non-terminals that do not share the same name as a property. In
       this case, the non-terminal name appears between "<" and ">", as in
       <border-width>. Notice the distinction between <border-width> and
       <'border-width'>; the latter is defined in terms of the former. The
       definition of a non-terminal is located near its first appearance
       in the specification. In the electronic version of the document,
       each instance of this type of value links to the corresponding
       value definition.

   Other words in these definitions are keywords that must appear
   literally, without quotes (e.g., red). The slash (/) and the comma (,)
   must also appear literally.

   Component values may be arranged into property values as follows:
     * Several juxtaposed words mean that all of them must occur, in the
       given order.
     * A bar (|) separates two or more alternatives: exactly one of them
       must occur.
     * A double bar (||) separates two or more options: one or more of
       them must occur, in any order.
     * A double ampersand (&&) separates two or more components, all of
       which must occur, in any order.
     * Brackets ([ ]) are for grouping.

   Juxtaposition is stronger than the double ampersand, the double
   ampersand is stronger than the double bar, and the double bar is
   stronger than the bar. Thus, the following lines are equivalent:
    a b   |   c ||   d &&   e f
  [ a b ] | [ c || [ d && [ e f ]]]

   Every type, keyword, or bracketed group may be followed by one of the
   following modifiers:
     * An asterisk (*) indicates that the preceding type, word, or group
       occurs zero or more times.
     * A plus (+) indicates that the preceding type, word, or group occurs
       one or more times.
     * A question mark (?) indicates that the preceding type, word, or
       group is optional.
     * A pair of numbers in curly braces ({A,B}) indicates that the
       preceding type, word, or group occurs at least A and at most B
       times.

   The following examples illustrate different value types:

     Value: N | NW | NE
     Value: [ <length> | thick | thin ]{1,4}
     Value: [<family-name> , ]* <family-name>
     Value: <uri>? <color> [ / <color> ]?
     Value: <uri> || <color>
     Value: inset? && [ <length>{2,4} && <color>? ]

   Component values are specified in terms of tokens, as described in
   Appendix G.2. As the grammar allows spaces between tokens in the
   components of the expr production, spaces may appear between tokens in
   property values.

   Note: In many cases, spaces will in fact be required between tokens in
   order to distinguish them from each other. For example, the value
   '1em2em' would be parsed as a single DIMEN token with the number '1'
   and the identifier 'em2em', which is an invalid unit. In this case, a
   space would be required before the '2' to get this parsed as the two
   lengths '1em' and '2em'.

    1.4.2.2 Initial

   This part specifies the property's initial value. Please consult the
   section on the cascade for information about the interaction between
   style sheet-specified, inherited, and initial property values.

    1.4.2.3 Applies to

   This part lists the elements to which the property applies. All
   elements are considered to have all properties, but some properties
   have no rendering effect on some types of elements. For example, the
   'clear' property only affects block-level elements.

    1.4.2.4 Inherited

   This part indicates whether the value of the property is inherited from
   an ancestor element. Please consult the section on the cascade for
   information about the interaction between style sheet-specified,
   inherited, and initial property values.

    1.4.2.5 Percentage values

   This part indicates how percentages should be interpreted, if they
   occur in the value of the property. If "N/A" appears here, it means
   that the property does not accept percentages in its values.

    1.4.2.6 Media groups

   This part indicates the media groups to which the property applies.
   Information about media groups is non-normative.

    1.4.2.7 Computed value

   This part describes the computed value for the property. See the
   section on computed values for how this definition is used.

  1.4.3 Shorthand properties

   Some properties are shorthand properties, meaning that they allow
   authors to specify the values of several properties with a single
   property.

   For instance, the 'font' property is a shorthand property for setting
   'font-style', 'font-variant', 'font-weight', 'font-size',
   'line-height', and 'font-family' all at once.

   When values are omitted from a shorthand form, each "missing" property
   is assigned its initial value (see the section on the cascade).

   Example(s):

   The multiple style rules of this example:
h1 {
  font-weight: bold;
  font-size: 12pt;
  line-height: 14pt;
  font-family: Helvetica;
  font-variant: normal;
  font-style: normal;
}

   may be rewritten with a single shorthand property:
h1 { font: bold 12pt/14pt Helvetica }

   In this example, 'font-variant', and 'font-style' take their initial
   values.

  1.4.4 Notes and examples

   All examples that illustrate illegal usage are clearly marked as
   "ILLEGAL EXAMPLE".

   HTML examples lacking DOCTYPE declarations are SGML Text Entities
   conforming to the HTML 4.01 Strict DTD [HTML4]. Other HTML examples
   conform to the DTDs given in the examples.

   All notes are informative only.

   Examples and notes are marked within the source HTML for the
   specification and CSS user agents will render them specially.

  1.4.5 Images and long descriptions

   Most images in the electronic version of this specification are
   accompanied by "long descriptions" of what they represent. A link to
   the long description is denoted by a "[D]" after the image.

   Images and long descriptions are informative only.

1.5 Acknowledgments

   This section is non-normative.

   CSS 2.1 is based on CSS2. See the acknowledgments section of CSS2 for
   the people that contributed to CSS2.

   We would like to thank the following people who, through their input
   and feedback on the www-style mailing list, have helped us with the
   creation of this specification: Andrew Clover, Bernd Mielke, C.
   Bottelier, Christian Roth, Christoph Päper, Claus Färber, Coises, Craig
   Saila, Darren Ferguson, Dylan Schiemann, Etan Wexler, George Lund,
   James Craig, Jan Eirik Olufsen, Jan Roland Eriksson, Joris Huizer,
   Joshua Prowse, Kai Lahmann, Kevin Smith, Lachlan Cannon, Lars Knoll,
   Lauri Raittila, Mark Gallagher, Michael Day, Peter Sheerin, Rijk van
   Geijtenbeek, Robin Berjon, Scott Montgomery, Shelby Moore, Stuart
   Ballard, Tom Gilder, Vadim Plessky, Peter Moulder, Anton Prowse, Gérard
   Talbot, Ingo Chao, Bruno Fassino, Justin Rogers, Boris Zbarsky, Garrett
   Smith, Zack Weinberg, Bjoern Hoehrmann, and the Open eBook Publication
   Structure Working Group Editors. We would also like to thank Gary
   Schnabl, Glenn Adams and Susan Lesch who helped proofread earlier
   versions of this document.

   In addition, we would like to extend special thanks to Elika J. Etemad,
   Ada Chan and Boris Zbarsky who have contributed significant time to
   CSS 2.1, and to Kimberly Blessing for help with the editing.

   Many thanks also to the following people for their help with the test
   suite: Robert Stam, Aharon Lanin, Alan Gresley, Alan Harder, Alexander
   Dawson, Arron Eicholz, Bernd Mielke, Bert Bos, Boris Zbarsky, Bruno
   Fassino, Daniel Schattenkirchner, David Hammond, David Hyatt, Eira
   Monstad, Elika J. Etemad, Gérard Talbot, Gabriele Romanato, Germain
   Garand, Hilbrand Edskes, Ian Hickson, James Hopkins, Justin Boss, L.
   David Baron, Lachlan Hunt, Magne Andersson, Marc Pacheco, Mark
   McKenzie-Bell, Matt Bradley, Melinda Grant, Michael Turnwall, Ray
   Kiddy, Richard Ishida, Robert O'Callahan, Simon Montagu, Tom Clancy,
   Vasil Dinkov, … and all the contributors to the CSS1 test suite.

   Working Group members active during the development of this
   specification: César Acebal (Universidad de Oviedo), Tab Atkins Jr.
   (Google, Inc.), L. David Baron (Mozilla Foundation), Bert Bos
   (W3C/ERCIM), Tantek Çelik (W3C Invited Experts), Cathy Chan (Nokia),
   Giorgi Chavchanidze (Opera Software), John Daggett (Mozilla
   Foundation), Beth Dakin (Apple, Inc.), Arron Eicholz (Microsoft Corp.),
   Elika J. Etemad (W3C Invited Experts), Simon Fraser (Apple, Inc.),
   Sylvain Galineau (Microsoft Corp.), Daniel Glazman (Disruptive
   Innovations), Molly Holzschlag (Opera Software), David Hyatt (Apple,
   Inc.), Richard Ishida (W3C/ERCIM), John Jansen (Microsoft Corp.), Brad
   Kemper (W3C Invited Experts), Håkon Wium Lie (Opera Software), Chris
   Lilley (W3C/ERCIM), Peter Linss (HP), Markus Mielke (Microsoft Corp.),
   Alex Mogilevsky (Microsoft Corp.), David Singer (Apple Inc.), Anne van
   Kesteren (Opera Software), Steve Zilles (Adobe Systems Inc.), Ian
   Hickson (Google, Inc.), Melinda Grant (HP), Øyvind Stenhaug (Opera
   Software), and Paul Nelson (Microsoft Corp.).

                           2 Introduction to CSS 2.1

   Contents
     * 2.1 A brief CSS 2.1 tutorial for HTML
     * 2.2 A brief CSS 2.1 tutorial for XML
     * 2.3 The CSS 2.1 processing model
          + 2.3.1 The canvas
          + 2.3.2 CSS 2.1 addressing model
     * 2.4 CSS design principles

2.1 A brief CSS 2.1 tutorial for HTML

   This section is non-normative.

   In this tutorial, we show how easy it can be to design simple style
   sheets. For this tutorial, you will need to know a little HTML (see
   [HTML4]) and some basic desktop publishing terminology.

   We begin with a small HTML document:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
  <TITLE>Bach's home page</TITLE>
  </HEAD>
  <BODY>
    <H1>Bach's home page</H1>
    <P>Johann Sebastian Bach was a prolific composer.
  </BODY>
</HTML>

   To set the text color of the H1 elements to red, you can write the
   following CSS rules:
  h1 { color: red }

   A CSS rule consists of two main parts: selector ('h1') and declaration
   ('color: red'). In HTML, element names are case-insensitive so 'h1'
   works just as well as 'H1'. The declaration has two parts: property
   name ('color') and property value ('red'). While the example above
   tries to influence only one of the properties needed for rendering an
   HTML document, it qualifies as a style sheet on its own. Combined with
   other style sheets (one fundamental feature of CSS is that style sheets
   are combined), the rule will determine the final presentation of the
   document.

   The HTML 4 specification defines how style sheet rules may be specified
   for HTML documents: either within the HTML document, or via an external
   style sheet. To put the style sheet into the document, use the STYLE
   element:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
  <TITLE>Bach's home page</TITLE>
  <STYLE type="text/css">
    h1 { color: red }
  </STYLE>
  </HEAD>
  <BODY>
    <H1>Bach's home page</H1>
    <P>Johann Sebastian Bach was a prolific composer.
  </BODY>
</HTML>

   For maximum flexibility, we recommend that authors specify external
   style sheets; they may be changed without modifying the source HTML
   document, and they may be shared among several documents. To link to an
   external style sheet, you can use the LINK element:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
  <TITLE>Bach's home page</TITLE>
  <LINK rel="stylesheet" href="bach.css" type="text/css">
  </HEAD>
  <BODY>
    <H1>Bach's home page</H1>
    <P>Johann Sebastian Bach was a prolific composer.
  </BODY>
</HTML>

   The LINK element specifies:
     * the type of link: to a "stylesheet".
     * the location of the style sheet via the "href" attribute.
     * the type of style sheet being linked: "text/css".

   To show the close relationship between a style sheet and the structured
   markup, we continue to use the STYLE element in this tutorial. Let's
   add more colors:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
  <TITLE>Bach's home page</TITLE>
  <STYLE type="text/css">
    body { color: black; background: white }
    h1 { color: red; background: white }
  </STYLE>
  </HEAD>
  <BODY>
    <H1>Bach's home page</H1>
    <P>Johann Sebastian Bach was a prolific composer.
  </BODY>
</HTML>

   The style sheet now contains four rules: the first two set the color
   and background of the BODY element (it's a good idea to set the text
   color and background color together), while the last two set the color
   and the background of the H1 element. Since no color has been specified
   for the P element, it will inherit the color from its parent element,
   namely BODY. The H1 element is also a child element of BODY but the
   second rule overrides the inherited value. In CSS there are often such
   conflicts between different values, and this specification describes
   how to resolve them.

   CSS 2.1 has more than 90 properties, including 'color'. Let's look at
   some of the others:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
  <TITLE>Bach's home page</TITLE>
  <STYLE type="text/css">
    body {
      font-family: "Gill Sans", sans-serif;
      font-size: 12pt;
      margin: 3em;
    }
  </STYLE>
  </HEAD>
  <BODY>
    <H1>Bach's home page</H1>
    <P>Johann Sebastian Bach was a prolific composer.
  </BODY>
</HTML>

   The first thing to notice is that several declarations are grouped
   within a block enclosed by curly braces ({...}), and separated by
   semicolons, though the last declaration may also be followed by a
   semicolon.

   The first declaration on the BODY element sets the font family to "Gill
   Sans". If that font is not available, the user agent (often referred to
   as a "browser") will use the 'sans-serif' font family which is one of
   five generic font families which all users agents know. Child elements
   of BODY will inherit the value of the 'font-family' property.

   The second declaration sets the font size of the BODY element to 12
   points. The "point" unit is commonly used in print-based typography to
   indicate font sizes and other length values. It's an example of an
   absolute unit which does not scale relative to the environment.

   The third declaration uses a relative unit which scales with regard to
   its surroundings. The "em" unit refers to the font size of the element.
   In this case the result is that the margins around the BODY element are
   three times wider than the font size.

2.2 A brief CSS 2.1 tutorial for XML

   This section is non-normative.

   CSS can be used with any structured document format, for example with
   applications of the eXtensible Markup Language [XML10]. In fact, XML
   depends more on style sheets than HTML, since authors can make up their
   own elements that user agents do not know how to display.

   Here is a simple XML fragment:
<ARTICLE>
  <HEADLINE>Fredrick the Great meets Bach</HEADLINE>
  <AUTHOR>Johann Nikolaus Forkel</AUTHOR>
  <PARA>
    One evening, just as he was getting his
    <INSTRUMENT>flute</INSTRUMENT> ready and his
    musicians were assembled, an officer brought him a list of
    the strangers who had arrived.
  </PARA>
</ARTICLE>

   To display this fragment in a document-like fashion, we must first
   declare which elements are inline-level (i.e., do not cause line
   breaks) and which are block-level (i.e., cause line breaks).
INSTRUMENT { display: inline }
ARTICLE, HEADLINE, AUTHOR, PARA { display: block }

   The first rule declares INSTRUMENT to be inline and the second rule,
   with its comma-separated list of selectors, declares all the other
   elements to be block-level. Element names in XML are case-sensitive, so
   a selector written in lowercase (e.g., 'instrument') is different from
   uppercase (e.g., 'INSTRUMENT').

   One way of linking a style sheet to an XML document is to use a
   processing instruction:
<?xml-stylesheet type="text/css" href="bach.css"?>
<ARTICLE>
  <HEADLINE>Fredrick the Great meets Bach</HEADLINE>
  <AUTHOR>Johann Nikolaus Forkel</AUTHOR>
  <PARA>
    One evening, just as he was getting his
    <INSTRUMENT>flute</INSTRUMENT> ready and his
    musicians were assembled, an officer brought him a list of
    the strangers who had arrived.
  </PARA>
</ARTICLE>

   A visual user agent could format the above example as:

   Example rendering    [D]

   Notice that the word "flute" remains within the paragraph since it is
   the content of the inline element INSTRUMENT.

   Still, the text is not formatted the way you would expect. For example,
   the headline font size should be larger than then the rest of the text,
   and you may want to display the author's name in italic:
INSTRUMENT { display: inline }
ARTICLE, HEADLINE, AUTHOR, PARA { display: block }
HEADLINE { font-size: 1.3em }
AUTHOR { font-style: italic }
ARTICLE, HEADLINE, AUTHOR, PARA { margin: 0.5em }

   A visual user agent could format the above example as:

   Example rendering    [D]

   Adding more rules to the style sheet will allow you to further describe
   the presentation of the document.

2.3 The CSS 2.1 processing model

   This section up to but not including its subsections is non-normative.

   This section presents one possible model of how user agents that
   support CSS work. This is only a conceptual model; real implementations
   may vary.

   In this model, a user agent processes a source by going through the
   following steps:
    1. Parse the source document and create a document tree.
    2. Identify the target media type.
    3. Retrieve all style sheets associated with the document that are
       specified for the target media type.
    4. Annotate every element of the document tree by assigning a single
       value to every property that is applicable to the target media
       type. Properties are assigned values according to the mechanisms
       described in the section on cascading and inheritance.
       Part of the calculation of values depends on the formatting
       algorithm appropriate for the target media type. For example, if
       the target medium is the screen, user agents apply the visual
       formatting model.
    5. From the annotated document tree, generate a formatting structure.
       Often, the formatting structure closely resembles the document
       tree, but it may also differ significantly, notably when authors
       make use of pseudo-elements and generated content. First, the
       formatting structure need not be "tree-shaped" at all -- the nature
       of the structure depends on the implementation. Second, the
       formatting structure may contain more or less information than the
       document tree. For instance, if an element in the document tree has
       a value of 'none' for the 'display' property, that element will
       generate nothing in the formatting structure. A list element, on
       the other hand, may generate more information in the formatting
       structure: the list element's content and list style information
       (e.g., a bullet image).
       Note that the CSS user agent does not alter the document tree
       during this phase. In particular, content generated due to style
       sheets is not fed back to the document language processor (e.g.,
       for reparsing).
    6. Transfer the formatting structure to the target medium (e.g., print
       the results, display them on the screen, render them as speech,
       etc.).

  2.3.1 The canvas

   For all media, the term canvas describes "the space where the
   formatting structure is rendered." The canvas is infinite for each
   dimension of the space, but rendering generally occurs within a finite
   region of the canvas, established by the user agent according to the
   target medium. For instance, user agents rendering to a screen
   generally impose a minimum width and choose an initial width based on
   the dimensions of the viewport. User agents rendering to a page
   generally impose width and height constraints. Aural user agents may
   impose limits in audio space, but not in time.

  2.3.2 CSS 2.1 addressing model

   CSS 2.1 selectors and properties allow style sheets to refer to the
   following parts of a document or user agent:
     * Elements in the document tree and certain relationships between
       them (see the section on selectors).
     * Attributes of elements in the document tree, and values of those
       attributes (see the section on attribute selectors).
     * Some parts of element content (see the :first-line and
       :first-letter pseudo-elements).
     * Elements of the document tree when they are in a certain state (see
       the section on pseudo-classes).
     * Some aspects of the canvas where the document will be rendered.
     * Some system information (see the section on user interface).

2.4 CSS design principles

   This section is non-normative.

   CSS 2.1, as CSS2 and CSS1 before it, is based on a set of design
   principles:
     * Forward and backward compatibility. CSS 2.1 user agents will be
       able to understand CSS1 style sheets. CSS1 user agents will be able
       to read CSS 2.1 style sheets and discard parts they do not
       understand. Also, user agents with no CSS support will be able to
       display style-enhanced documents. Of course, the stylistic
       enhancements made possible by CSS will not be rendered, but all
       content will be presented.
     * Complementary to structured documents. Style sheets complement
       structured documents (e.g., HTML and XML applications), providing
       stylistic information for the marked-up text. It should be easy to
       change the style sheet with little or no impact on the markup.
     * Vendor, platform, and device independence. Style sheets enable
       documents to remain vendor, platform, and device independent. Style
       sheets themselves are also vendor and platform independent, but
       CSS 2.1 allows you to target a style sheet for a group of devices
       (e.g., printers).
     * Maintainability. By pointing to style sheets from documents,
       webmasters can simplify site maintenance and retain consistent look
       and feel throughout the site. For example, if the organization's
       background color changes, only one file needs to be changed.
     * Simplicity. CSS is a simple style language which is human readable
       and writable. The CSS properties are kept independent of each other
       to the largest extent possible and there is generally only one way
       to achieve a certain effect.
     * Network performance. CSS provides for compact encodings of how to
       present content. Compared to images or audio files, which are often
       used by authors to achieve certain rendering effects, style sheets
       most often decrease the content size. Also, fewer network
       connections have to be opened which further increases network
       performance.
     * Flexibility. CSS can be applied to content in several ways. The key
       feature is the ability to cascade style information specified in
       the default (user agent) style sheet, user style sheets, linked
       style sheets, the document head, and in attributes for the elements
       forming the document body.
     * Richness. Providing authors with a rich set of rendering effects
       increases the richness of the Web as a medium of expression.
       Designers have been longing for functionality commonly found in
       desktop publishing and slide-show applications. Some of the
       requested rendering effects conflict with device independence, but
       CSS 2.1 goes a long way toward granting designers their requests.
     * Alternative language bindings. The set of CSS properties described
       in this specification form a consistent formatting model for visual
       and aural presentations. This formatting model can be accessed
       through the CSS language, but bindings to other languages are also
       possible. For example, a JavaScript program may dynamically change
       the value of a certain element's 'color' property.
     * Accessibility. Several CSS features will make the Web more
       accessible to users with disabilities:
          + Properties to control font appearance allow authors to
            eliminate inaccessible bit-mapped text images.
          + Positioning properties allow authors to eliminate mark-up
            tricks (e.g., invisible images) to force layout.
          + The semantics of !important rules mean that users with
            particular presentation requirements can override the author's
            style sheets.
          + The 'inherit' value for all properties improves cascading
            generality and allows for easier and more consistent style
            tuning.
          + Improved media support, including media groups and the
            braille, embossed, and tty media types, will allow users and
            authors to tailor pages to those devices.
       Note. For more information about designing accessible documents
       using CSS and HTML, see [[-WCAG20]].

                3 Conformance: Requirements and Recommendations

   Contents
     * 3.1 Definitions
     * 3.2 UA Conformance
     * 3.3 Error conditions
     * 3.4 The text/css content type

3.1 Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 (see
   [RFC2119]). However, for readability, these words do not appear in all
   uppercase letters in this specification.

   At times, this specification recommends good practice for authors and
   user agents. These recommendations are not normative and conformance
   with this specification does not depend on their realization. These
   recommendations contain the expression "We recommend ...", "This
   specification recommends ...", or some similar wording.

   The fact that a feature is marked as deprecated (namely the 'aural'
   keyword) or going to be deprecated in CSS3 (namely the system colors)
   also has no influence on conformance. (For example, 'aural' is marked
   as non-normative, so UAs do not need to support it; the system colors
   are normative, so UAs must support them.)

   All sections of this specification, including appendices, are normative
   unless otherwise noted.

   Examples and notes are not normative.

   Example(s):

   Examples usually have the word "example" near their start ("Example:",
   "The following example…," "For example," etc.) and are shown in the
   color maroon, like this paragraph.

   Notes start with the word "Note," are indented and shown in green, like
   this paragraph.

   Figures are for illustration only. They are not reference renderings,
   unless explicitly stated.

   Style sheet
          A set of statements that specify presentation of a document.

          Style sheets may have three different origins: author, user, and
          user agent. The interaction of these sources is described in the
          section on cascading and inheritance.

   Valid style sheet
          The validity of a style sheet depends on the level of CSS used
          for the style sheet. All valid CSS1 style sheets are valid
          CSS 2.1 style sheets, but some changes from CSS1 mean that a few
          CSS1 style sheets will have slightly different semantics in
          CSS 2.1. Some features in CSS2 are not part of CSS 2.1, so not
          all CSS2 style sheets are valid CSS 2.1 style sheets.

          A valid CSS 2.1 style sheet must be written according to the
          grammar of CSS 2.1. Furthermore, it must contain only at-rules,
          property names, and property values defined in this
          specification. An illegal (invalid) at-rule, property name, or
          property value is one that is not valid.

   Source document
          The document to which one or more style sheets apply. This is
          encoded in some language that represents the document as a tree
          of elements. Each element consists of a name that identifies the
          type of element, optionally a number of attributes, and a
          (possibly empty) content. For example, the source document could
          be an XML or SGML instance.

   Document language
          The encoding language of the source document (e.g., HTML, XHTML,
          or SVG). CSS is used to describe the presentation of document
          languages and CSS does not change the underlying semantics of
          the document languages.

   Element
          (An SGML term, see [ISO8879].) The primary syntactic constructs
          of the document language. Most CSS style sheet rules use the
          names of these elements (such as P, TABLE, and OL in HTML) to
          specify how the elements should be rendered.

   Replaced element
          An element whose content is outside the scope of the CSS
          formatting model, such as an image, embedded document, or
          applet. For example, the content of the HTML IMG element is
          often replaced by the image that its "src" attribute designates.
          Replaced elements often have intrinsic dimensions: an intrinsic
          width, an intrinsic height, and an intrinsic ratio. For example,
          a bitmap image has an intrinsic width and an intrinsic height
          specified in absolute units (from which the intrinsic ratio can
          obviously be determined). On the other hand, other documents may
          not have any intrinsic dimensions (for example, a blank HTML
          document).

          User agents may consider a replaced element to not have any
          intrinsic dimensions if it is believed that those dimensions
          could leak sensitive information to a third party. For example,
          if an HTML document changed intrinsic size depending on the
          user's bank balance, then the UA might want to act as if that
          resource had no intrinsic dimensions.

          The content of replaced elements is not considered in the CSS
          rendering model.

   Intrinsic dimensions
          The width and height as defined by the element itself, not
          imposed by the surroundings. CSS does not define how the
          intrinsic dimensions are found. In CSS 2.1 only replaced
          elements can come with intrinsic dimensions. For raster images
          without reliable resolution information, a size of 1 px unit per
          image source pixel must be assumed.

   Attribute
          A value associated with an element, consisting of a name, and an
          associated (textual) value.

   Content
          The content associated with an element in the source document.
          Some elements have no content, in which case they are called
          empty. The content of an element may include text, and it may
          include a number of sub-elements, in which case the element is
          called the parent of those sub-elements.

   Ignore
          This term has two slightly different meanings in this
          specification. First, a CSS parser must follow certain rules
          when it discovers unknown or illegal syntax in a style sheet.
          The parser must then ignore certain parts of the style sheets.
          The exact rules for which parts must be ignored are described in
          these sections (Declarations and properties, Rules for handling
          parsing errors, Unsupported Values) or may be explained in the
          text where the term "ignore" appears. Second, a user agent may
          (and, in some cases must) disregard certain properties or values
          in the style sheet, even if the syntax is legal. For example,
          table-column elements cannot affect the font of the column, so
          the font properties must be ignored.

   Rendered content
          The content of an element after the rendering that applies to it
          according to the relevant style sheets has been applied. How a
          replaced element's content is rendered is not defined by this
          specification. Rendered content may also be alternate text for
          an element (e.g., the value of the XHTML "alt" attribute), and
          may include items inserted implicitly or explicitly by the style
          sheet, such as bullets, numbering, etc.

   Document tree
          The tree of elements encoded in the source document. Each
          element in this tree has exactly one parent, with the exception
          of the root element, which has none.

   Child
          An element A is called the child of element B if and only if B
          is the parent of A.

   Descendant
          An element A is called a descendant of an element B, if either
          (1) A is a child of B, or (2) A is the child of some element C
          that is a descendant of B.

   Ancestor
          An element A is called an ancestor of an element B, if and only
          if B is a descendant of A.

   Sibling
          An element A is called a sibling of an element B, if and only if
          B and A share the same parent element. Element A is a preceding
          sibling if it comes before B in the document tree. Element B is
          a following sibling if it comes after A in the document tree.

   Preceding element
          An element A is called a preceding element of an element B, if
          and only if (1) A is an ancestor of B or (2) A is a preceding
          sibling of B.

   Following element
          An element A is called a following element of an element B, if
          and only if B is a preceding element of A.

   Author
          An author is a person who writes documents and associated style
          sheets. An authoring tool is a User Agent that generates style
          sheets.

   User
          A user is a person who interacts with a user agent to view,
          hear, or otherwise use a document and its associated style
          sheet. The user may provide a personal style sheet that encodes
          personal preferences.

   User agent (UA)
          A user agent is any program that interprets a document written
          in the document language and applies associated style sheets
          according to the terms of this specification. A user agent may
          display a document, read it aloud, cause it to be printed,
          convert it to another format, etc.
          An HTML user agent is one that supports one or more of the HTML
          specifications. A user agent that supports XHTML [XHTML], but
          not HTML is not considered an HTML user agent for the purpose of
          conformance with this specification.

   Property
          CSS defines a finite set of parameters, called properties, that
          direct the rendering of a document. Each property has a name
          (e.g., 'color', 'font', or border') and a value (e.g., 'red',
          '12pt Times', or 'dotted'). Properties are attached to various
          parts of the document and to the page on which the document is
          to be displayed by the mechanisms of specificity, cascading, and
          inheritance (see the chapter on Assigning property values,
          Cascading, and Inheritance).

   Here is an example of a source document written in HTML:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <TITLE>My home page</TITLE>
  <BODY>
    <H1>My home page</H1>
    <P>Welcome to my home page! Let me tell you about my favorite
                composers:
    <UL>
      <LI> Elvis Costello
      <LI> Johannes Brahms
      <LI> Georges Brassens
    </UL>
  </BODY>
</HTML>

   This results in the following tree:

   Sample document tree    [D]

   According to the definition of HTML 4, HEAD elements will be inferred
   during parsing and become part of the document tree even if the "head"
   tags are not in the document source. Similarly, the parser knows where
   the P and LI elements end, even though there are no </p> and </li> tags
   in the source.

   Documents written in XHTML (and other XML-based languages) behave
   differently: there are no inferred elements and all elements must have
   end tags.

3.2 UA Conformance

   This section defines conformance with the CSS 2.1 specification only.
   There may be other levels of CSS in the future that may require a user
   agent to implement a different set of features in order to conform.

   In general, the following points must be observed by a user agent
   claiming conformance to this specification:
    1. It must recognize one or more of the CSS 2.1 media types.
    2. For each source document, it must attempt to retrieve all
       associated style sheets that are appropriate for the recognized
       media types. If it cannot retrieve all associated style sheets (for
       instance, because of network errors), it must display the document
       using those it can retrieve.
    3. It must parse the style sheets according to this specification. In
       particular, it must recognize all at-rules, blocks, declarations,
       and selectors (see the grammar of CSS 2.1). If a user agent
       encounters a property that applies for a supported media type, the
       user agent must parse the value according to the property
       definition. This means that the user agent must accept all valid
       values and must ignore declarations with invalid values. User
       agents must ignore rules that apply to unsupported media types.
    4. For each element in a document tree, it must assign a value for
       every property according to the property's definition and the rules
       of cascading and inheritance.
    5. If the source document comes with alternate style sheet sets (such
       as with the "alternate" keyword in HTML 4 [HTML4]), the UA must
       allow the user to select which style sheet set the UA should apply.
    6. The UA must allow the user to turn off the influence of author
       style sheets.

   Not every user agent must observe every point, however:
     * An application that reads style sheets without rendering any
       content (e.g., a CSS 2.1 validator) must respect points 1-3.
     * An authoring tool is only required to output valid style sheets
     * A user agent that renders a document with associated style sheets
       must respect points 1-6 and render the document according to the
       media-specific requirements set forth in this specification. Values
       may be approximated when required by the user agent.

   The inability of a user agent to implement part of this specification
   due to the limitations of a particular device (e.g., a user agent
   cannot render colors on a monochrome monitor or page) does not imply
   non-conformance.

   UAs must allow users to specify a file that contains the user style
   sheet. UAs that run on devices without any means of writing or
   specifying files are exempted from this requirement. Additionally, UAs
   may offer other means to specify user preferences, for example, through
   a GUI.

   CSS 2.1 does not define which properties apply to form controls and
   frames, or how CSS can be used to style them. User agents may apply CSS
   properties to these elements. Authors are recommended to treat such
   support as experimental. A future level of CSS may specify this
   further.

3.3 Error conditions

   In general, this document specifies error handling behavior throughout
   the specification. For example, see the rules for handling parsing
   errors.

3.4 The text/css content type

   CSS style sheets that exist in separate files are sent over the
   Internet as a sequence of bytes accompanied by encoding information.
   The structure of the transmission, termed a message entity, is defined
   by RFC 2045 and RFC 2616 (see [RFC2045] and [RFC2616]). A message
   entity with a content type of "text/css" represents an independent CSS
   document. The "text/css" content type has been registered by RFC 2318
   ([RFC2318]).

                         4 Syntax and basic data types

   Contents
     * 4.1 Syntax
          + 4.1.1 Tokenization
          + 4.1.2 Keywords
               o 4.1.2.1 Vendor-specific extensions
               o 4.1.2.2 Informative Historical Notes
          + 4.1.3 Characters and case
          + 4.1.4 Statements
          + 4.1.5 At-rules
          + 4.1.6 Blocks
          + 4.1.7 Rule sets, declaration blocks, and selectors
          + 4.1.8 Declarations and properties
          + 4.1.9 Comments
     * 4.2 Rules for handling parsing errors
     * 4.3 Values
          + 4.3.1 Integers and real numbers
          + 4.3.2 Lengths
          + 4.3.3 Percentages
          + 4.3.4 URLs and URIs
          + 4.3.5 Counters
          + 4.3.6 Colors
          + 4.3.7 Strings
          + 4.3.8 Unsupported Values
     * 4.4 CSS style sheet representation
          + 4.4.1 Referring to characters not represented in a character
            encoding

4.1 Syntax

   This section describes a grammar (and forward-compatible parsing rules)
   common to any level of CSS (including CSS 2.1). Future updates of CSS
   will adhere to this core syntax, although they may add additional
   syntactic constraints.

   These descriptions are normative. They are also complemented by the
   normative grammar rules presented in Appendix G.

   In this specification, the expressions "immediately before" or
   "immediately after" mean with no intervening white space or comments.

  4.1.1 Tokenization

   All levels of CSS — level 1, level 2, and any future levels — use the
   same core syntax. This allows UAs to parse (though not completely
   understand) style sheets written in levels of CSS that did not exist at
   the time the UAs were created. Designers can use this feature to create
   style sheets that work with older user agents, while also exercising
   the possibilities of the latest levels of CSS.

   At the lexical level, CSS style sheets consist of a sequence of tokens.
   The list of tokens for CSS is as follows. The definitions use Lex-style
   regular expressions. Octal codes refer to ISO 10646 ([ISO10646]). As in
   Lex, in case of multiple matches, the longest match determines the
   token.

     Token                                Definition
   __________________________________________________________________

 IDENT         {ident}
 ATKEYWORD     @{ident}
 STRING        {string}
 BAD_STRING    {badstring}
 BAD_URI       {baduri}
 BAD_COMMENT   {badcomment}
 HASH          #{name}
 NUMBER        {num}
 PERCENTAGE    {num}%
 DIMENSION     {num}{ident}
 URI           url\({w}{string}{w}\)
               |url\({w}([!#$%&*-\[\]-~]|{nonascii}|{escape})*{w}\)
 UNICODE-RANGE u\+[0-9a-f?]{1,6}(-[0-9a-f]{1,6})?
 CDO           <!--
 CDC           -->
 :             :
 ;             ;
 {             \{
 }             \}
 (             \(
 )             \)
 [             \[
 ]             \]
 S             [ \t\r\n\f]+
 COMMENT       \/\*[^*]*\*+([^/*][^*]*\*+)*\/
 FUNCTION      {ident}\(
 INCLUDES      ~=
 DASHMATCH     |=
 DELIM         any other character not matched by the above rules, and neither a
               single nor a double quote

   The macros in curly braces ({}) above are defined as follows:

      Macro                          Definition
     __________________________________________________________________

   ident       [-]?{nmstart}{nmchar}*
   name        {nmchar}+
   nmstart     [_a-z]|{nonascii}|{escape}
   nonascii    [^\0-\237]
   unicode     \\[0-9a-f]{1,6}(\r\n|[ \n\r\t\f])?
   escape      {unicode}|\\[^\n\r\f0-9a-f]
   nmchar      [_a-z0-9-]|{nonascii}|{escape}
   num         [0-9]+|[0-9]*\.[0-9]+
   string      {string1}|{string2}
   string1     \"([^\n\r\f\\"]|\\{nl}|{escape})*\"
   string2     \'([^\n\r\f\\']|\\{nl}|{escape})*\'
   badstring   {badstring1}|{badstring2}
   badstring1  \"([^\n\r\f\\"]|\\{nl}|{escape})*\\?
   badstring2  \'([^\n\r\f\\']|\\{nl}|{escape})*\\?
   badcomment  {badcomment1}|{badcomment2}
   badcomment1 \/\*[^*]*\*+([^/*][^*]*\*+)*
   badcomment2 \/\*[^*]*(\*+[^/*][^*]*)*
   baduri      {baduri1}|{baduri2}|{baduri3}
   baduri1     url\({w}([!#$%&*-~]|{nonascii}|{escape})*{w}
   baduri2     url\({w}{string}{w}
   baduri3     url\({w}{badstring}
   nl          \n|\r\n|\r|\f
   w           [ \t\r\n\f]*

   Example(s):

   For example, the rule of the longest match means that "red-->" is
   tokenized as the IDENT "red--" followed by the DELIM ">", rather than
   as an IDENT followed by a CDC.

   Below is the core syntax for CSS. The sections that follow describe how
   to use it. Appendix G describes a more restrictive grammar that is
   closer to the CSS level 2 language. Parts of style sheets that can be
   parsed according to this grammar but not according to the grammar in
   Appendix G are among the parts that will be ignored according to the
   rules for handling parsing errors.
stylesheet  : [ CDO | CDC | S | statement ]*;
statement   : ruleset | at-rule;
at-rule     : ATKEYWORD S* any* [ block | ';' S* ];
block       : '{' S* [ any | block | ATKEYWORD S* | ';' S* ]* '}' S*;
ruleset     : selector? '{' S* declaration? [ ';' S* declaration? ]* '}' S*;
selector    : any+;
declaration : property S* ':' S* value;
property    : IDENT;
value       : [ any | block | ATKEYWORD S* ]+;
any         : [ IDENT | NUMBER | PERCENTAGE | DIMENSION | STRING
              | DELIM | URI | HASH | UNICODE-RANGE | INCLUDES
              | DASHMATCH | ':' | FUNCTION S* [any|unused]* ')'
              | '(' S* [any|unused]* ')' | '[' S* [any|unused]* ']'
              ] S*;
unused      : block | ATKEYWORD S* | ';' S* | CDO S* | CDC S*;

   The "unused" production is not used in CSS and will not be used by any
   future extension. It is included here only to help with error handling.
   (See 4.2 "Rules for handling parsing errors.")

   COMMENT tokens do not occur in the grammar (to keep it readable), but
   any number of these tokens may appear anywhere outside other tokens.
   (Note, however, that a comment before or within the @charset rule
   disables the @charset.)

   The token S in the grammar above stands for white space. Only the
   characters "space" (U+0020), "tab" (U+0009), "line feed" (U+000A),
   "carriage return" (U+000D), and "form feed" (U+000C) can occur in white
   space. Other space-like characters, such as "em-space" (U+2003) and
   "ideographic space" (U+3000), are never part of white space.

   The meaning of input that cannot be tokenized or parsed is undefined in
   CSS 2.1.

  4.1.2 Keywords

   Keywords have the form of identifiers. Keywords must not be placed
   between quotes ("..." or '...'). Thus,
red

   is a keyword, but
"red"

   is not. (It is a string.) Other illegal examples:

   Illegal example(s):
width: "auto";
border: "none";
background: "red";

    4.1.2.1 Vendor-specific extensions

   In CSS, identifiers may begin with '-' (dash) or '_' (underscore).
   Keywords and property names beginning with -' or '_' are reserved for
   vendor-specific extensions. Such vendor-specific extensions should have
   one of the following formats:
'-' + vendor identifier + '-' + meaningful name
'_' + vendor identifier + '-' + meaningful name

   Example(s):

   For example, if XYZ organization added a property to describe the color
   of the border on the East side of the display, they might call it
   -xyz-border-east-color.

   Other known examples:
-moz-box-sizing
-moz-border-radius
-wap-accesskey

   An initial dash or underscore is guaranteed never to be used in a
   property or keyword by any current or future level of CSS. Thus typical
   CSS implementations may not recognize such properties and may ignore
   them according to the rules for handling parsing errors. However,
   because the initial dash or underscore is part of the grammar, CSS 2.1
   implementers should always be able to use a CSS-conforming parser,
   whether or not they support any vendor-specific extensions.

   Authors should avoid vendor-specific extensions

    4.1.2.2 Informative Historical Notes

   This section is informative.

   At the time of writing, the following prefixes are known to exist:

     prefix                organization
   -ms-, mso- Microsoft
   -moz-      Mozilla
   -o-, -xv-  Opera Software
   -atsc-     Advanced Television Standards Committee
   -wap-      The WAP Forum
   -khtml-    KDE
   -webkit-   Apple
   prince-    YesLogic
   -ah-       Antenna House
   -hp-       Hewlett Packard
   -ro-       Real Objects
   -rim-      Research In Motion
   -tc-       TallComponents

  4.1.3 Characters and case

   The following rules always hold:
     * All CSS syntax is case-insensitive within the ASCII range (i.e.,
       [a-z] and [A-Z] are equivalent), except for parts that are not
       under the control of CSS. For example, the case-sensitivity of
       values of the HTML attributes "id" and "class", of font names, and
       of URIs lies outside the scope of this specification. Note in
       particular that element names are case-insensitive in HTML, but
       case-sensitive in XML.
     * In CSS, identifiers (including element names, classes, and IDs in
       selectors) can contain only the characters [a-zA-Z0-9] and ISO
       10646 characters U+00A0 and higher, plus the hyphen (-) and the
       underscore (_); they cannot start with a digit, two hyphens, or a
       hyphen followed by a digit. Identifiers can also contain escaped
       characters and any ISO 10646 character as a numeric code (see next
       item). For instance, the identifier "B&W?" may be written as
       "B\&W\?" or "B\26 W\3F".
       Note that Unicode is code-by-code equivalent to ISO 10646 (see
       [UNICODE] and [ISO10646]).
     * In CSS 2.1, a backslash (\) character can indicate one of three
       types of character escape. Inside a CSS comment, a backslash stands
       for itself, and if a backslash is immediately followed by the end
       of the style sheet, it also stands for itself (i.e., a DELIM
       token).
       First, inside a string, a backslash followed by a newline is
       ignored (i.e., the string is deemed not to contain either the
       backslash or the newline). Outside a string, a backslash followed
       by a newline stands for itself (i.e., a DELIM followed by a
       newline).
       Second, it cancels the meaning of special CSS characters. Any
       character (except a hexadecimal digit, linefeed, carriage return,
       or form feed) can be escaped with a backslash to remove its special
       meaning. For example, "\"" is a string consisting of one double
       quote. Style sheet preprocessors must not remove these backslashes
       from a style sheet since that would change the style sheet's
       meaning.
       Third, backslash escapes allow authors to refer to characters they
       cannot easily put in a document. In this case, the backslash is
       followed by at most six hexadecimal digits (0..9A..F), which stand
       for the ISO 10646 ([ISO10646]) character with that number, which
       must not be zero. (It is undefined in CSS 2.1 what happens if a
       style sheet does contain a character with Unicode codepoint zero.)
       If a character in the range [0-9a-fA-F] follows the hexadecimal
       number, the end of the number needs to be made clear. There are two
       ways to do that:
         1. with a space (or other white space character): "\26 B" ("&B").
            In this case, user agents should treat a "CR/LF" pair
            (U+000D/U+000A) as a single white space character.
         2. by providing exactly 6 hexadecimal digits: "\000026B" ("&B")
       In fact, these two methods may be combined. Only one white space
       character is ignored after a hexadecimal escape. Note that this
       means that a "real" space after the escape sequence must be
       doubled.
       If the number is outside the range allowed by Unicode (e.g.,
       "\110000" is above the maximum 10FFFF allowed in current Unicode),
       the UA may replace the escape with the "replacement character"
       (U+FFFD). If the character is to be displayed, the UA should show a
       visible symbol, such as a "missing character" glyph (cf. 15.2,
       point 5).
     * Note: Backslash escapes are always considered to be part of an
       identifier or a string (i.e., "\7B" is not punctuation, even though
       "{" is, and "\32" is allowed at the start of a class name, even
       though "2" is not).
       The identifier "te\st" is exactly the same identifier as "test".

  4.1.4 Statements

   A CSS style sheet, for any level of CSS, consists of a list of
   statements (see the grammar above). There are two kinds of statements:
   at-rules and rule sets. There may be white space around the statements.

  4.1.5 At-rules

   At-rules start with an at-keyword, an '@' character followed
   immediately by an identifier (for example, '@import', '@page').

   An at-rule consists of everything up to and including the next
   semicolon (;) or the next block, whichever comes first.

   CSS 2.1 user agents must ignore any '@import' rule that occurs inside a
   block or after any non-ignored statement other than an @charset or an
   @import rule.

   Illegal example(s):

   Assume, for example, that a CSS 2.1 parser encounters this style sheet:
@import "subs.css";
h1 { color: blue }
@import "list.css";

   The second '@import' is illegal according to CSS 2.1. The CSS 2.1
   parser ignores the whole at-rule, effectively reducing the style sheet
   to:
@import "subs.css";
h1 { color: blue }

   Illegal example(s):

   In the following example, the second '@import' rule is invalid, since
   it occurs inside a '@media' block.
@import "subs.css";
@media print {
  @import "print-main.css";
  body { font-size: 10pt }
}
h1 {color: blue }

   Instead, to achieve the effect of only importing a style sheet for
   'print' media, use the @import rule with media syntax, e.g.:
@import "subs.css";
@import "print-main.css" print;
@media print {
  body { font-size: 10pt }
}
h1 {color: blue }

  4.1.6 Blocks

   A block starts with a left curly brace ({) and ends with the matching
   right curly brace (}). In between there may be any tokens, except that
   parentheses (( )), brackets ([ ]), and braces ({ }) must always occur
   in matching pairs and may be nested. Single (') and double quotes (")
   must also occur in matching pairs, and characters between them are
   parsed as a string. See Tokenization above for the definition of a
   string.

   Illegal example(s):

   Here is an example of a block. Note that the right brace between the
   double quotes does not match the opening brace of the block, and that
   the second single quote is an escaped character, and thus does not
   match the first single quote:
{ causta: "}" + ({7} * '\'') }

   Note that the above rule is not valid CSS 2.1, but it is still a block
   as defined above.

  4.1.7 Rule sets, declaration blocks, and selectors

   A rule set (also called "rule") consists of a selector followed by a
   declaration block.

   A declaration block starts with a left curly brace ({) and ends with
   the matching right curly brace (}). In between there must be a list of
   zero or more semicolon-separated (;) declarations.

   The selector (see also the section on selectors) consists of everything
   up to (but not including) the first left curly brace ({). A selector
   always goes together with a declaration block. When a user agent cannot
   parse the selector (i.e., it is not valid CSS 2.1), it must ignore the
   selector and the following declaration block (if any) as well.

   CSS 2.1 gives a special meaning to the comma (,) in selectors. However,
   since it is not known if the comma may acquire other meanings in future
   updates of CSS, the whole statement should be ignored if there is an
   error anywhere in the selector, even though the rest of the selector
   may look reasonable in CSS 2.1.

   Illegal example(s):

   For example, since the "&" is not a valid token in a CSS 2.1 selector,
   a CSS 2.1 user agent must ignore the whole second line, and not set the
   color of H3 to red:
h1, h2 {color: green }
h3, h4 & h5 {color: red }
h6 {color: black }

   Example(s):

   Here is a more complex example. The first two pairs of curly braces are
   inside a string, and do not mark the end of the selector. This is a
   valid CSS 2.1 rule.
p[example="public class foo\
{\
    private int x;\
\
    foo(int x) {\
        this.x = x;\
    }\
\
}"] { color: red }

  4.1.8 Declarations and properties

   A declaration is either empty or consists of a property name, followed
   by a colon (:), followed by a property value. Around each of these
   there may be white space.

   Because of the way selectors work, multiple declarations for the same
   selector may be organized into semicolon (;) separated groups.

   Example(s):

   Thus, the following rules:
h1 { font-weight: bold }
h1 { font-size: 12px }
h1 { line-height: 14px }
h1 { font-family: Helvetica }
h1 { font-variant: normal }
h1 { font-style: normal }

   are equivalent to:
h1 {
  font-weight: bold;
  font-size: 12px;
  line-height: 14px;
  font-family: Helvetica;
  font-variant: normal;
  font-style: normal
}

   A property name is an identifier. Any token may occur in the property
   value. Parentheses ("( )"), brackets ("[ ]"), braces ("{ }"), single
   quotes ('), and double quotes (") must come in matching pairs, and
   semicolons not in strings must be escaped. Parentheses, brackets, and
   braces may be nested. Inside the quotes, characters are parsed as a
   string.

   The syntax of values is specified separately for each property, but in
   any case, values are built from identifiers, strings, numbers, lengths,
   percentages, URIs, colors, etc.

   A user agent must ignore a declaration with an invalid property name or
   an invalid value. Every CSS property has its own syntactic and semantic
   restrictions on the values it accepts.

   Illegal example(s):

   For example, assume a CSS 2.1 parser encounters this style sheet:
h1 { color: red; font-style: 12pt }  /* Invalid value: 12pt */
p { color: blue;  font-vendor: any;  /* Invalid prop.: font-vendor */
    font-variant: small-caps }
em em { font-style: normal }

   The second declaration on the first line has an invalid value '12pt'.
   The second declaration on the second line contains an undefined
   property 'font-vendor'. The CSS 2.1 parser will ignore these
   declarations, effectively reducing the style sheet to:
h1 { color: red; }
p { color: blue;  font-variant: small-caps }
em em { font-style: normal }

  4.1.9 Comments

   Comments begin with the characters "/*" and end with the characters
   "*/". They may occur anywhere outside other tokens, and their contents
   have no influence on the rendering. Comments may not be nested.

   CSS also allows the SGML comment delimiters ("<!--" and "-->") in
   certain places defined by the grammar, but they do not delimit CSS
   comments. They are permitted so that style rules appearing in an HTML
   source document (in the STYLE element) may be hidden from pre-HTML 3.2
   user agents. See the HTML 4 specification ([HTML4]) for more
   information.

4.2 Rules for handling parsing errors

   In some cases, user agents must ignore part of an illegal style sheet.
   This specification defines ignore to mean that the user agent parses
   the illegal part (in order to find its beginning and end), but
   otherwise acts as if it had not been there. CSS 2.1 reserves for future
   updates of CSS all property:value combinations and @-keywords that do
   not contain an identifier beginning with dash or underscore.
   Implementations must ignore such combinations (other than those
   introduced by future updates of CSS).

   To ensure that new properties and new values for existing properties
   can be added in the future, user agents are required to obey the
   following rules when they encounter the following scenarios:
     * Unknown properties. User agents must ignore a declaration with an
       unknown property. For example, if the style sheet is:
h1 { color: red; rotation: 70minutes }

       the user agent will treat this as if the style sheet had been
h1 { color: red }

     * Illegal values. User agents must ignore a declaration with an
       illegal value. For example:
img { float: left }       /* correct CSS 2.1 */
img { float: left here }  /* "here" is not a value of 'float' */
img { background: "red" } /* keywords cannot be quoted */
img { border-width: 3 }   /* a unit must be specified for length values */

       A CSS 2.1 parser would honor the first rule and ignore the rest, as
       if the style sheet had been:
img { float: left }
img { }
img { }
img { }

       A user agent conforming to a future CSS specification may accept
       one or more of the other rules as well.
     * Malformed declarations. User agents must handle unexpected tokens
       encountered while parsing a declaration by reading until the end of
       the declaration, while observing the rules for matching pairs of
       (), [], {}, "", and '', and correctly handling escapes. For
       example, a malformed declaration may be missing a property name,
       colon (:), or property value. The following are all equivalent:
p { color:green }
p { color:green; color }  /* malformed declaration missing ':', value */
p { color:red;   color; color:green }  /* same with expected recovery */
p { color:green; color: } /* malformed declaration missing value */
p { color:red;   color:; color:green } /* same with expected recovery */
p { color:green; color{;color:maroon} } /* unexpected tokens { } */
p { color:red;   color{;color:maroon}; color:green } /* same with recovery */

     * Malformed statements. User agents must handle unexpected tokens
       encountered while parsing a statement by reading until the end of
       the statement, while observing the rules for matching pairs of (),
       [], {}, "", and '', and correctly handling escapes. For example, a
       malformed statement may contain an unexpected closing brace or
       at-keyword. E.g., the following lines are all ignored:
p @here {color: red}     /* ruleset with unexpected at-keyword "@here" */
@foo @bar;               /* at-rule with unexpected at-keyword "@bar" */
}} {{ - }}               /* ruleset with unexpected right brace */
) ( {} ) p {color: red } /* ruleset with unexpected right parenthesis */

     * At-rules with unknown at-keywords. User agents must ignore an
       invalid at-keyword together with everything following it, up to the
       end of the block that contains the invalid at-keyword, or up to and
       including the next semicolon (;), or up to and including the next
       block ({...}), whichever comes first. For example, consider the
       following:
@three-dee {
  @background-lighting {
    azimuth: 30deg;
    elevation: 190deg;
  }
  h1 { color: red }
}
h1 { color: blue }

       The '@three-dee' at-rule is not part of CSS 2.1. Therefore, the
       whole at-rule (up to, and including, the third right curly brace)
       is ignored. A CSS 2.1 user agent ignores it, effectively reducing
       the style sheet to:
h1 { color: blue }

       Something inside an at-rule that is ignored because it is invalid,
       such as an invalid declaration within an @media-rule, does not make
       the entire at-rule invalid.
     * Unexpected end of style sheet.
       User agents must close all open constructs (for example: blocks,
       parentheses, brackets, rules, strings, and comments) at the end of
       the style sheet. For example:
  @media screen {
    p:before { content: 'Hello

       would be treated the same as:
  @media screen {
    p:before { content: 'Hello'; }
  }

       in a conformant UA.
     * Unexpected end of string.
       User agents must close strings upon reaching the end of a line
       (i.e., before an unescaped line feed, carriage return or form feed
       character), but then drop the construct (declaration or rule) in
       which the string was found. For example:
      p {
        color: green;
        font-family: 'Courier New Times
        color: red;
        color: green;
      }

       ...would be treated the same as:
      p { color: green; color: green; }

       ...because the second declaration (from 'font-family' to the
       semicolon after 'color: red') is invalid and is dropped.
     * See also Rule sets, declaration blocks, and selectors for parsing
       rules for declaration blocks.

4.3 Values

  4.3.1 Integers and real numbers

   Some value types may have integer values (denoted by <integer>) or real
   number values (denoted by <number>). Real numbers and integers are
   specified in decimal notation only. An <integer> consists of one or
   more digits "0" to "9". A <number> can either be an <integer>, or it
   can be zero or more digits followed by a dot (.) followed by one or
   more digits. Both integers and real numbers may be preceded by a "-" or
   "+" to indicate the sign. -0 is equivalent to 0 and is not a negative
   number.

   Note that many properties that allow an integer or real number as a
   value actually restrict the value to some range, often to a
   non-negative value.

  4.3.2 Lengths

   Lengths refer to distance measurements.

   The format of a length value (denoted by <length> in this
   specification) is a <number> (with or without a decimal point)
   immediately followed by a unit identifier (e.g., px, em, etc.). After a
   zero length, the unit identifier is optional.

   Some properties allow negative length values, but this may complicate
   the formatting model and there may be implementation-specific limits.
   If a negative length value cannot be supported, it should be converted
   to the nearest value that can be supported.

   If a negative length value is set on a property that does not allow
   negative length values, the declaration is ignored.

   In cases where the used length cannot be supported, user agents must
   approximate it in the actual value.

   There are two types of length units: relative and absolute. Relative
   length units specify a length relative to another length property.
   Style sheets that use relative units can more easily scale from one
   output environment to another.

   Relative units are:
     * em: the 'font-size' of the relevant font
     * ex: the 'x-height' of the relevant font

   Example(s):
h1 { margin: 0.5em }      /* em */
h1 { margin: 1ex }        /* ex */

   The 'em' unit is equal to the computed value of the 'font-size'
   property of the element on which it is used. The exception is when 'em'
   occurs in the value of the 'font-size' property itself, in which case
   it refers to the font size of the parent element. It may be used for
   vertical or horizontal measurement. (This unit is also sometimes called
   the quad-width in typographic texts.)

   The 'ex' unit is defined by the element's first available font. The
   exception is when 'ex' occurs in the value of the 'font-size' property,
   in which case it refers to the 'ex' of the parent element.

   The 'x-height' is so called because it is often equal to the height of
   the lowercase "x". However, an 'ex' is defined even for fonts that do
   not contain an "x".

   The x-height of a font can be found in different ways. Some fonts
   contain reliable metrics for the x-height. If reliable font metrics are
   not available, UAs may determine the x-height from the height of a
   lowercase glyph. One possible heuristic is to look at how far the glyph
   for the lowercase "o" extends below the baseline, and subtract that
   value from the top of its bounding box. In the cases where it is
   impossible or impractical to determine the x-height, a value of 0.5em
   should be used.

   Example(s):

   The rule:
h1 { line-height: 1.2em }

   means that the line height of "h1" elements will be 20% greater than
   the font size of the "h1" elements. On the other hand:
h1 { font-size: 1.2em }

   means that the font-size of "h1" elements will be 20% greater than the
   font size inherited by "h1" elements.

   When specified for the root of the document tree (e.g., "HTML" in
   HTML), 'em' and 'ex' refer to the property's initial value.

   Child elements do not inherit the relative values specified for their
   parent; they inherit the computed values.

   Example(s):

   In the following rules, the computed 'text-indent' value of "h1"
   elements will be 36px, not 45px, if "h1" is a child of the "body"
   element.
body {
  font-size: 12px;
  text-indent: 3em;  /* i.e., 36px */
}
h1 { font-size: 15px }

   Absolute length units are fixed in relation to each other. They are
   mainly useful when the output environment is known. The absolute units
   consist of the physical units (in, cm, mm, pt, pc) and the px unit:
     * in: inches — 1in is equal to 2.54cm.
     * cm: centimeters
     * mm: millimeters
     * pt: points — the points used by CSS are equal to 1/72nd of 1in.
     * pc: picas — 1pc is equal to 12pt.
     * px: pixel units — 1px is equal to 0.75pt.

   For a CSS device, these dimensions are either anchored (i) by relating
   the physical units to their physical measurements, or (ii) by relating
   the pixel unit to the reference pixel. For print media and similar
   high-resolution devices, the anchor unit should be one of the standard
   physical units (inches, centimeters, etc). For lower-resolution
   devices, and devices with unusual viewing distances, it is recommended
   instead that the anchor unit be the pixel unit. For such devices it is
   recommended that the pixel unit refer to the whole number of device
   pixels that best approximates the reference pixel.

   Note that if the anchor unit is the pixel unit, the physical units
   might not match their physical measurements. Alternatively if the
   anchor unit is a physical unit, the pixel unit might not map to a whole
   number of device pixels.

   Note that this definition of the pixel unit and the physical units
   differs from previous versions of CSS. In particular, in previous
   versions of CSS the pixel unit and the physical units were not related
   by a fixed ratio: the physical units were always tied to their physical
   measurements while the pixel unit would vary to most closely match the
   reference pixel. (This change was made because too much existing
   content relies on the assumption of 96dpi, and breaking that assumption
   breaks the content.)

   The reference pixel is the visual angle of one pixel on a device with a
   pixel density of 96dpi and a distance from the reader of an arm's
   length. For a nominal arm's length of 28 inches, the visual angle is
   therefore about 0.0213 degrees. For reading at arm's length, 1px thus
   corresponds to about 0.26 mm (1/96 inch).

   The image below illustrates the effect of viewing distance on the size
   of a reference pixel: a reading distance of 71 cm (28 inches) results
   in a reference pixel of 0.26 mm, while a reading distance of 3.5 m
   (12 feet) results in a reference pixel of 1.3 mm.

   Showing that pixels must become larger if the viewing distance
   increases    [D]

   This second image illustrates the effect of a device's resolution on
   the pixel unit: an area of 1px by 1px is covered by a single dot in a
   low-resolution device (e.g. a typical computer display), while the same
   area is covered by 16 dots in a higher resolution device (such as a
   printer).

   Showing that more device pixels (dots) are needed to cover a 1px by 1px
   area on a high-resolution device than on a low-res one    [D]

   Example(s):
h1 { margin: 0.5in }      /* inches  */
h2 { line-height: 3cm }   /* centimeters */
h3 { word-spacing: 4mm }  /* millimeters */
h4 { font-size: 12pt }    /* points */
h4 { font-size: 1pc }     /* picas */
p  { font-size: 12px }    /* px */

  4.3.3 Percentages

   The format of a percentage value (denoted by <percentage> in this
   specification) is a <number> immediately followed by '%'.

   Percentage values are always relative to another value, for example a
   length. Each property that allows percentages also defines the value to
   which the percentage refers. The value may be that of another property
   for the same element, a property for an ancestor element, or a value of
   the formatting context (e.g., the width of a containing block). When a
   percentage value is set for a property of the root element and the
   percentage is defined as referring to the inherited value of some
   property, the resultant value is the percentage times the initial value
   of that property.

   Example(s):

   Since child elements (generally) inherit the computed values of their
   parent, in the following example, the children of the P element will
   inherit a value of 12px for 'line-height', not the percentage value
   (120%):
p { font-size: 10px }
p { line-height: 120% }  /* 120% of 'font-size' */

  4.3.4 URLs and URIs

   URI values (Uniform Resource Identifiers, see [RFC3986], which includes
   URLs, URNs, etc) in this specification are denoted by <uri>. The
   functional notation used to designate URIs in property values is
   "url()", as in:

   Example(s):
body { background: url("http://www.example.com/pinkish.png") }

   The format of a URI value is 'url(' followed by optional white space
   followed by an optional single quote (') or double quote (") character
   followed by the URI itself, followed by an optional single quote (') or
   double quote (") character followed by optional white space followed by
   ')'. The two quote characters must be the same.

   Example(s):

   An example without quotes:
li { list-style: url(http://www.example.com/redball.png) disc }

   Some characters appearing in an unquoted URI, such as parentheses,
   white space characters, single quotes (') and double quotes ("), must
   be escaped with a backslash so that the resulting URI value is a URI
   token: '\(', '\)'.

   Depending on the type of URI, it might also be possible to write the
   above characters as URI-escapes (where "(" = %28, ")" = %29, etc.) as
   described in [RFC3986].

   Note that COMMENT tokens cannot occur within other tokens: thus,
   "url(/*x*/pic.png)" denotes the URI "/*x*/pic.png", not "pic.png".

   In order to create modular style sheets that are not dependent on the
   absolute location of a resource, authors may use relative URIs.
   Relative URIs (as defined in [RFC3986]) are resolved to full URIs using
   a base URI. RFC 3986, section 5, defines the normative algorithm for
   this process. For CSS style sheets, the base URI is that of the style
   sheet, not that of the source document.

   Example(s):

   For example, suppose the following rule:
body { background: url("yellow") }

   is located in a style sheet designated by the URI:
http://www.example.org/style/basic.css

   The background of the source document's BODY will be tiled with
   whatever image is described by the resource designated by the URI
http://www.example.org/style/yellow

   User agents may vary in how they handle invalid URIs or URIs that
   designate unavailable or inapplicable resources.

  4.3.5 Counters

   Counters are denoted by case-sensitive identifiers (see the
   'counter-increment' and 'counter-reset' properties). To refer to the
   value of a counter, the notation 'counter(<identifier>)' or
   'counter(<identifier>, <'list-style-type'>)', with optional white space
   separating the tokens, is used. The default style is 'decimal'.

   To refer to a sequence of nested counters of the same name, the
   notation is 'counters(<identifier>, <string>)' or
   'counters(<identifier>, <string>, <'list-style-type'>)' with optional
   white space separating the tokens.

   See "Nested counters and scope" in the chapter on generated content for
   how user agents must determine the value or values of the counter. See
   the definition of counter values of the 'content' property for how it
   must convert these values to a string.

   In CSS 2.1, the values of counters can only be referred to from the
   'content' property. Note that 'none' is a possible <'list-style-type'>:
   'counter(x, none)' yields an empty string.

   Example(s):

   Here is a style sheet that numbers paragraphs (p) for each chapter
   (h1). The paragraphs are numbered with roman numerals, followed by a
   period and a space:
p {counter-increment: par-num}
h1 {counter-reset: par-num}
p:before {content: counter(par-num, upper-roman) ". "}

  4.3.6 Colors

   A <color> is either a keyword or a numerical RGB specification.

   The list of color keywords is: aqua, black, blue, fuchsia, gray, green,
   lime, maroon, navy, olive, orange, purple, red, silver, teal, white,
   and yellow. These 17 colors have the following values:

   maroon #800000 red #ff0000 orange #ffA500 yellow #ffff00 olive #808000
   purple #800080 fuchsia #ff00ff white #ffffff lime #00ff00 green #008000
   navy #000080 blue #0000ff aqua #00ffff teal #008080
   black #000000 silver #c0c0c0 gray #808080

   In addition to these color keywords, users may specify keywords that
   correspond to the colors used by certain objects in the user's
   environment. Please consult the section on system colors for more
   information.

   Example(s):
body {color: black; background: white }
h1 { color: maroon }
h2 { color: olive }

   The RGB color model is used in numerical color specifications. These
   examples all specify the same color:

   Example(s):
em { color: #f00 }              /* #rgb */
em { color: #ff0000 }           /* #rrggbb */
em { color: rgb(255,0,0) }
em { color: rgb(100%, 0%, 0%) }

   The format of an RGB value in hexadecimal notation is a '#' immediately
   followed by either three or six hexadecimal characters. The three-digit
   RGB notation (#rgb) is converted into six-digit form (#rrggbb) by
   replicating digits, not by adding zeros. For example, #fb0 expands to
   #ffbb00. This ensures that white (#ffffff) can be specified with the
   short notation (#fff) and removes any dependencies on the color depth
   of the display.

   The format of an RGB value in the functional notation is 'rgb('
   followed by a comma-separated list of three numerical values (either
   three integer values or three percentage values) followed by ')'. The
   integer value 255 corresponds to 100%, and to F or FF in the
   hexadecimal notation: rgb(255,255,255) = rgb(100%,100%,100%) = #FFF.
   White space characters are allowed around the numerical values.

   All RGB colors are specified in the sRGB color space (see [SRGB]). User
   agents may vary in the fidelity with which they represent these colors,
   but using sRGB provides an unambiguous and objectively measurable
   definition of what the color should be, which can be related to
   international standards (see [COLORIMETRY]).

   Conforming user agents may limit their color-displaying efforts to
   performing a gamma-correction on them. sRGB specifies a display gamma
   of 2.2 under specified viewing conditions. User agents should adjust
   the colors given in CSS such that, in combination with an output
   device's "natural" display gamma, an effective display gamma of 2.2 is
   produced. Note that only colors specified in CSS are affected; e.g.,
   images are expected to carry their own color information.

   Values outside the device gamut should be clipped or mapped into the
   gamut when the gamut is known: the red, green, and blue values must be
   changed to fall within the range supported by the device. Users agents
   may perform higher quality mapping of colors from one gamut to another.
   For a typical CRT monitor, whose device gamut is the same as sRGB, the
   four rules below are equivalent:

   Example(s):
em { color: rgb(255,0,0) }       /* integer range 0 - 255 */
em { color: rgb(300,0,0) }       /* clipped to rgb(255,0,0) */
em { color: rgb(255,-10,0) }     /* clipped to rgb(255,0,0) */
em { color: rgb(110%, 0%, 0%) }  /* clipped to rgb(100%,0%,0%) */

   Other devices, such as printers, have different gamuts than sRGB; some
   colors outside the 0..255 sRGB range will be representable (inside the
   device gamut), while other colors inside the 0..255 sRGB range will be
   outside the device gamut and will thus be mapped.

   Note. Mapping or clipping of color values should be done to the actual
   device gamut if known (which may be larger or smaller than 0..255).

  4.3.7 Strings

   Strings can either be written with double quotes or with single quotes.
   Double quotes cannot occur inside double quotes, unless escaped (e.g.,
   as '\"' or as '\22'). Analogously for single quotes (e.g., "\'" or
   "\27").

   Example(s):
"this is a 'string'"
"this is a \"string\""
'this is a "string"'
'this is a \'string\''

   A string cannot directly contain a newline. To include a newline in a
   string, use an escape representing the line feed character in ISO-10646
   (U+000A), such as "\A" or "\00000a". This character represents the
   generic notion of "newline" in CSS. See the 'content' property for an
   example.

   It is possible to break strings over several lines, for aesthetic or
   other reasons, but in such a case the newline itself has to be escaped
   with a backslash (\). For instance, the following two selectors are
   exactly the same:

   Example(s):
a[title="a not s\
o very long title"] {/*...*/}
a[title="a not so very long title"] {/*...*/}

  4.3.8 Unsupported Values

   If a UA does not support a particular value, it should ignore that
   value when parsing style sheets, as if that value was an illegal value.
   For example:

   Example(s):
  h3 {
    display: inline;
    display: run-in;
  }

   A UA that supports the 'run-in' value for the 'display' property will
   accept the first display declaration and then "write over" that value
   with the second display declaration. A UA that does not support the
   'run-in' value will process the first display declaration and ignore
   the second display declaration.

4.4 CSS style sheet representation

   A CSS style sheet is a sequence of characters from the Universal
   Character Set (see [ISO10646]). For transmission and storage, these
   characters must be encoded by a character encoding that supports the
   set of characters available in US-ASCII (e.g., UTF-8, ISO 8859-x, SHIFT
   JIS, etc.). For a good introduction to character sets and character
   encodings, please consult the HTML 4 specification ([HTML4], chapter
   5). See also the XML 1.0 specification ([XML10], sections 2.2 and
   4.3.3, and Appendix F).

   When a style sheet is embedded in another document, such as in the
   STYLE element or "style" attribute of HTML, the style sheet shares the
   character encoding of the whole document.

   When a style sheet resides in a separate file, user agents must observe
   the following priorities when determining a style sheet's character
   encoding (from highest priority to lowest):
    1. An HTTP "charset" parameter in a "Content-Type" field (or similar
       parameters in other protocols)
    2. BOM and/or @charset (see below)
    3. <link charset=""> or other metadata from the linking mechanism (if
       any)
    4. charset of referring style sheet or document (if any)
    5. Assume UTF-8

   Authors using an @charset rule must place the rule at the very
   beginning of the style sheet, preceded by no characters. (If a byte
   order mark is appropriate for the encoding used, it may precede the
   @charset rule.)

   After "@charset", authors specify the name of a character encoding (in
   quotes). For example:
@charset "ISO-8859-1";

   @charset must be written literally, i.e., the 10 characters '@charset
   "' (lowercase, no backslash escapes), followed by the encoding name,
   followed by '";'.

   The name must be a charset name as described in the IANA registry. See
   [CHARSETS] for a complete list of charsets. Authors should use the
   charset names marked as "preferred MIME name" in the IANA registry.

   User agents must support at least the UTF-8 encoding.

   User agents must ignore any @charset rule not at the beginning of the
   style sheet. When user agents detect the character encoding using the
   BOM and/or the @charset rule, they should follow the following rules:
     * Except as specified in these rules, all @charset rules are ignored.
     * The encoding is detected based on the stream of bytes that begins
       the style sheet. The following table gives a set of possibilities
       for initial byte sequences (written in hexadecimal). The first row
       that matches the beginning of the style sheet gives the result of
       encoding detection based on the BOM and/or @charset rule. If no
       rows match, the encoding cannot be detected based on the BOM and/or
       @charset rule. The notation (...)* refers to repetition for which
       the best match is the one that repeats as few times as possible.
       The bytes marked "XX" are those used to determine the name of the
       encoding, by treating them, in the order given, as a sequence of
       ASCII characters. Bytes marked "YY" are similar, but need to be
       transcoded into ASCII as noted. User agents may ignore entries in
       the table if they do not support any encodings relevant to the
       entry.

   Initial Bytes Result
   EF BB BF 40 63 68 61 72 73 65 74 20 22 (XX)* 22 3B as specified
   EF BB BF UTF-8
   40 63 68 61 72 73 65 74 20 22 (XX)* 22 3B as specified
   FE FF 00 40 00 63 00 68 00 61 00 72 00 73 00 65 00 74 00 20 00 22 (00
   XX)* 00 22 00 3B as specified (with BE endianness if not specified)
   00 40 00 63 00 68 00 61 00 72 00 73 00 65 00 74 00 20 00 22 (00 XX)* 00
   22 00 3B as specified (with BE endianness if not specified)
   FF FE 40 00 63 00 68 00 61 00 72 00 73 00 65 00 74 00 20 00 22 00 (XX
   00)* 22 00 3B 00 as specified (with LE endianness if not specified)
   40 00 63 00 68 00 61 00 72 00 73 00 65 00 74 00 20 00 22 00 (XX 00)* 22
   00 3B 00 as specified (with LE endianness if not specified)
   00 00 FE FF 00 00 00 40 00 00 00 63 00 00 00 68 00 00 00 61 00 00 00 72
   00 00 00 73 00 00 00 65 00 00 00 74 00 00 00 20 00 00 00 22 (00 00 00
   XX)* 00 00 00 22 00 00 00 3B as specified (with BE endianness if not
   specified)
   00 00 00 40 00 00 00 63 00 00 00 68 00 00 00 61 00 00 00 72 00 00 00 73
   00 00 00 65 00 00 00 74 00 00 00 20 00 00 00 22 (00 00 00 XX)* 00 00 00
   22 00 00 00 3B as specified (with BE endianness if not specified)
   00 00 FF FE 00 00 40 00 00 00 63 00 00 00 68 00 00 00 61 00 00 00 72 00
   00 00 73 00 00 00 65 00 00 00 74 00 00 00 20 00 00 00 22 00 (00 00 XX
   00)* 00 00 22 00 00 00 3B 00 as specified (with 2143 endianness if not
   specified)
   00 00 40 00 00 00 63 00 00 00 68 00 00 00 61 00 00 00 72 00 00 00 73 00
   00 00 65 00 00 00 74 00 00 00 20 00 00 00 22 00 (00 00 XX 00)* 00 00 22
   00 00 00 3B 00 as specified (with 2143 endianness if not specified)
   FE FF 00 00 00 40 00 00 00 63 00 00 00 68 00 00 00 61 00 00 00 72 00 00
   00 73 00 00 00 65 00 00 00 74 00 00 00 20 00 00 00 22 00 00 (00 XX 00
   00)* 00 22 00 00 00 3B 00 00 as specified (with 3412 endianness if not
   specified)
   00 40 00 00 00 63 00 00 00 68 00 00 00 61 00 00 00 72 00 00 00 73 00 00
   00 65 00 00 00 74 00 00 00 20 00 00 00 22 00 00 (00 XX 00 00)* 00 22 00
   00 00 3B 00 00 as specified (with 3412 endianness if not specified)
   FF FE 00 00 40 00 00 00 63 00 00 00 68 00 00 00 61 00 00 00 72 00 00 00
   73 00 00 00 65 00 00 00 74 00 00 00 20 00 00 00 22 00 00 00 (XX 00 00
   00)* 22 00 00 00 3B 00 00 00 as specified (with LE endianness if not
   specified)
   40 00 00 00 63 00 00 00 68 00 00 00 61 00 00 00 72 00 00 00 73 00 00 00
   65 00 00 00 74 00 00 00 20 00 00 00 22 00 00 00 (XX 00 00 00)* 22 00 00
   00 3B 00 00 00 as specified (with LE endianness if not specified)
   00 00 FE FF UTF-32-BE
   FF FE 00 00 UTF-32-LE
   00 00 FF FE UTF-32-2143
   FE FF 00 00 UTF-32-3412
   FE FF UTF-16-BE
   FF FE UTF-16-LE
   7C 83 88 81 99 A2 85 A3 40 7F (YY)* 7F 5E as specified, transcoded from
   EBCDIC to ASCII
   AE 83 88 81 99 A2 85 A3 40 FC (YY)* FC 5E as specified, transcoded from
   IBM1026 to ASCII
   00 63 68 61 72 73 65 74 20 22 (YY)* 22 3B as specified, transcoded from
   GSM 03.38 to ASCII
   analogous patterns User agents may support additional, analogous,
   patterns if they support encodings that are not handled by the patterns
   here
     * If the encoding is detected based on one of the entries in the
       table above marked "as specified", the user agent ignores the style
       sheet if it does not parse an appropriate @charset rule at the
       beginning of the stream of characters resulting from decoding in
       the chosen @charset. This ensures that:
          + @charset rules should only function if they are in the
            encoding of the style sheet,
          + byte order marks are ignored only in encodings that support a
            byte order mark, and
          + encoding names cannot contain newlines.

   User agents must ignore style sheets in unknown encodings.

  4.4.1 Referring to characters not represented in a character encoding

   A style sheet may have to refer to characters that cannot be
   represented in the current character encoding. These characters must be
   written as escaped references to ISO 10646 characters. These escapes
   serve the same purpose as numeric character references in HTML or XML
   documents (see [HTML4], chapters 5 and 25).

   The character escape mechanism should be used when only a few
   characters must be represented this way. If most of a style sheet
   requires escaping, authors should encode it with a more appropriate
   encoding (e.g., if the style sheet contains a lot of Greek characters,
   authors might use "ISO-8859-7" or "UTF-8").

   Intermediate processors using a different character encoding may
   translate these escaped sequences into byte sequences of that encoding.
   Intermediate processors must not, on the other hand, alter escape
   sequences that cancel the special meaning of an ASCII character.

   Conforming user agents must correctly map to ISO-10646 all characters
   in any character encodings that they recognize (or they must behave as
   if they did).

   For example, a style sheet transmitted as ISO-8859-1 (Latin-1) cannot
   contain Greek letters directly: "κουρος" (Greek: "kouros") has to be
   written as "\3BA\3BF\3C5\3C1\3BF\3C2".

   Note. In HTML 4, numeric character references are interpreted in
   "style" attribute values but not in the content of the STYLE element.
   Because of this asymmetry, we recommend that authors use the CSS
   character escape mechanism rather than numeric character references for
   both the "style" attribute and the STYLE element. For example, we
   recommend:
<SPAN style="font-family: L\FC beck">...</SPAN>

   rather than:
<SPAN style="font-family: L&#252;beck">...</SPAN>

                                  5 Selectors

   Contents
     * 5.1 Pattern matching
     * 5.2 Selector syntax
          + 5.2.1 Grouping
     * 5.3 Universal selector
     * 5.4 Type selectors
     * 5.5 Descendant selectors
     * 5.6 Child selectors
     * 5.7 Adjacent sibling selectors
     * 5.8 Attribute selectors
          + 5.8.1 Matching attributes and attribute values
          + 5.8.2 Default attribute values in DTDs
          + 5.8.3 Class selectors
     * 5.9 ID selectors
     * 5.10 Pseudo-elements and pseudo-classes
     * 5.11 Pseudo-classes
          + 5.11.1 :first-child pseudo-class
          + 5.11.2 The link pseudo-classes: :link and :visited
          + 5.11.3 The dynamic pseudo-classes: :hover, :active, and :focus
          + 5.11.4 The language pseudo-class: :lang
     * 5.12 Pseudo-elements
          + 5.12.1 The :first-line pseudo-element
          + 5.12.2 The :first-letter pseudo-element
          + 5.12.3 The :before and :after pseudo-elements

5.1 Pattern matching

   In CSS, pattern matching rules determine which style rules apply to
   elements in the document tree. These patterns, called selectors, may
   range from simple element names to rich contextual patterns. If all
   conditions in the pattern are true for a certain element, the selector
   matches the element.

   The case-sensitivity of document language element names in selectors
   depends on the document language. For example, in HTML, element names
   are case-insensitive, but in XML they are case-sensitive.

   The following table summarizes CSS 2.1 selector syntax:

   Pattern Meaning Described in section
   * Matches any element. Universal selector
   E Matches any E element (i.e., an element of type E). Type selectors
   E F Matches any F element that is a descendant of an E element.
   Descendant selectors
   E > F Matches any F element that is a child of an element E. Child
   selectors
   E:first-child Matches element E when E is the first child of its
   parent. The :first-child pseudo-class
   E:link
   E:visited Matches element E if E is the source anchor of a hyperlink of
   which the target is not yet visited (:link) or already visited
   (:visited). The link pseudo-classes
   E:active
   E:hover
   E:focus Matches E during certain user actions. The dynamic
   pseudo-classes
   E:lang(c) Matches element of type E if it is in (human) language c (the
   document language specifies how language is determined). The :lang()
   pseudo-class
   E + F Matches any F element immediately preceded by a sibling element
   E. Adjacent selectors
   E[foo] Matches any E element with the "foo" attribute set (whatever the
   value). Attribute selectors
   E[foo="warning"] Matches any E element whose "foo" attribute value is
   exactly equal to "warning". Attribute selectors
   E[foo~="warning"] Matches any E element whose "foo" attribute value is
   a list of space-separated values, one of which is exactly equal to
   "warning". Attribute selectors
   E[lang|="en"] Matches any E element whose "lang" attribute has a
   hyphen-separated list of values beginning (from the left) with "en".
   Attribute selectors
   DIV.warning Language specific. (In HTML, the same as
   DIV[class~="warning"].) Class selectors
   E#myid Matches any E element with ID equal to "myid". ID selectors

5.2 Selector syntax

   A simple selector is either a type selector or universal selector
   followed immediately by zero or more attribute selectors, ID selectors,
   or pseudo-classes, in any order. The simple selector matches if all of
   its components match.

   Note: the terminology used here in CSS 2.1 is different from what is
   used in CSS3. For example, a "simple selector" refers to a smaller part
   of a selector in CSS3 than in CSS 2.1. See the CSS3 Selectors module
   [CSS3SEL].

   A selector is a chain of one or more simple selectors separated by
   combinators. Combinators are: white space, ">", and "+". White space
   may appear between a combinator and the simple selectors around it.

   The elements of the document tree that match a selector are called
   subjects of the selector. A selector consisting of a single simple
   selector matches any element satisfying its requirements. Prepending a
   simple selector and combinator to a chain imposes additional matching
   constraints, so the subjects of a selector are always a subset of the
   elements matching the last simple selector.

   One pseudo-element may be appended to the last simple selector in a
   chain, in which case the style information applies to a subpart of each
   subject.

  5.2.1 Grouping

   When several selectors share the same declarations, they may be grouped
   into a comma-separated list.

   Example(s):

   In this example, we condense three rules with identical declarations
   into one. Thus,
h1 { font-family: sans-serif }
h2 { font-family: sans-serif }
h3 { font-family: sans-serif }

   is equivalent to:
h1, h2, h3 { font-family: sans-serif }

   CSS offers other "shorthand" mechanisms as well, including multiple
   declarations and shorthand properties.

5.3 Universal selector

   The universal selector, written "*", matches the name of any element
   type. It matches any single element in the document tree.

   If the universal selector is not the only component of a simple
   selector, the "*" may be omitted. For example:
     * *[lang=fr] and [lang=fr] are equivalent.
     * *.warning and .warning are equivalent.
     * *#myid and #myid are equivalent.

5.4 Type selectors

   A type selector matches the name of a document language element type. A
   type selector matches every instance of the element type in the
   document tree.

   Example(s):

   The following rule matches all H1 elements in the document tree:
h1 { font-family: sans-serif }

5.5 Descendant selectors

   At times, authors may want selectors to match an element that is the
   descendant of another element in the document tree (e.g., "Match those
   EM elements that are contained by an H1 element"). Descendant selectors
   express such a relationship in a pattern. A descendant selector is made
   up of two or more selectors separated by white space. A descendant
   selector of the form "A B" matches when an element B is an arbitrary
   descendant of some ancestor element A.

   Example(s):

   For example, consider the following rules:
h1 { color: red }
em { color: red }

   Although the intention of these rules is to add emphasis to text by
   changing its color, the effect will be lost in a case such as:
<H1>This headline is <EM>very</EM> important</H1>

   We address this case by supplementing the previous rules with a rule
   that sets the text color to blue whenever an EM occurs anywhere within
   an H1:
h1 { color: red }
em { color: red }
h1 em { color: blue }

   The third rule will match the EM in the following fragment:
<H1>This <SPAN class="myclass">headline
is <EM>very</EM> important</SPAN></H1>

   Example(s):

   The following selector:
div * p

   matches a P element that is a grandchild or later descendant of a DIV
   element. Note the white space on either side of the "*" is not part of
   the universal selector; the white space is a combinator indicating that
   the DIV must be the ancestor of some element, and that that element
   must be an ancestor of the P.

   Example(s):

   The selector in the following rule, which combines descendant and
   attribute selectors, matches any element that (1) has the "href"
   attribute set and (2) is inside a P that is itself inside a DIV:
div p *[href]

5.6 Child selectors

   A child selector matches when an element is the child of some element.
   A child selector is made up of two or more selectors separated by ">".

   Example(s):

   The following rule sets the style of all P elements that are children
   of BODY:
body > P { line-height: 1.3 }

   Example(s):

   The following example combines descendant selectors and child
   selectors:
div ol>li p

   It matches a P element that is a descendant of an LI; the LI element
   must be the child of an OL element; the OL element must be a descendant
   of a DIV. Notice that the optional white space around the ">"
   combinator has been left out.

   For information on selecting the first child of an element, please see
   the section on the :first-child pseudo-class below.

5.7 Adjacent sibling selectors

   Adjacent sibling selectors have the following syntax: E1 + E2, where E2
   is the subject of the selector. The selector matches if E1 and E2 share
   the same parent in the document tree and E1 immediately precedes E2,
   ignoring non-element nodes (such as text nodes and comments).

   Example(s):

   Thus, the following rule states that when a P element immediately
   follows a MATH element, it should not be indented:
math + p { text-indent: 0 }

   The next example reduces the vertical space separating an H1 and an H2
   that immediately follows it:
h1 + h2 { margin-top: -5mm }

   Example(s):

   The following rule is similar to the one in the previous example,
   except that it adds a class selector. Thus, special formatting only
   occurs when H1 has class="opener":
h1.opener + h2 { margin-top: -5mm }

5.8 Attribute selectors

   CSS 2.1 allows authors to specify rules that match elements which have
   certain attributes defined in the source document.

  5.8.1 Matching attributes and attribute values

   Attribute selectors may match in four ways:

   [att]
          Match when the element sets the "att" attribute, whatever the
          value of the attribute.

   [att=val]
          Match when the element's "att" attribute value is exactly "val".

   [att~=val]
          Represents an element with the att attribute whose value is a
          white space-separated list of words, one of which is exactly
          "val". If "val" contains white space, it will never represent
          anything (since the words are separated by spaces). If "val" is
          the empty string, it will never represent anything either.

   [att|=val]
          Represents an element with the att attribute, its value either
          being exactly "val" or beginning with "val" immediately followed
          by "-" (U+002D). This is primarily intended to allow language
          subcode matches (e.g., the hreflang attribute on the a element
          in HTML) as described in BCP 47 ([BCP47]) or its successor. For
          lang (or xml:lang) language subcode matching, please see the
          :lang pseudo-class.

   Attribute values must be identifiers or strings. The case-sensitivity
   of attribute names and values in selectors depends on the document
   language.

   Example(s):

   For example, the following attribute selector matches all H1 elements
   that specify the "title" attribute, whatever its value:
h1[title] { color: blue; }

   Example(s):

   In the following example, the selector matches all SPAN elements whose
   "class" attribute has exactly the value "example":
span[class=example] { color: blue; }

   Multiple attribute selectors can be used to refer to several attributes
   of an element, or even several times to the same attribute.

   Example(s):

   Here, the selector matches all SPAN elements whose "hello" attribute
   has exactly the value "Cleveland" and whose "goodbye" attribute has
   exactly the value "Columbus":
span[hello="Cleveland"][goodbye="Columbus"] { color: blue; }

   Example(s):

   The following selectors illustrate the differences between "=" and
   "~=". The first selector will match, for example, the value "copyright
   copyleft copyeditor" for the "rel" attribute. The second selector will
   only match when the "href" attribute has the value
   "http://www.w3.org/".
a[rel~="copyright"]
a[href="http://www.w3.org/"]

   Example(s):

   The following rule hides all elements for which the value of the "lang"
   attribute is "fr" (i.e., the language is French).
*[lang=fr] { display : none }

   Example(s):

   The following rule will match for values of the "lang" attribute that
   begin with "en", including "en", "en-US", and "en-cockney":
*[lang|="en"] { color : red }

   Example(s):

   Similarly, the following aural style sheet rules allow a script to be
   read aloud in different voices for each role:
DIALOGUE[character=romeo]
     { voice-family: "Laurence Olivier", charles, male }

DIALOGUE[character=juliet]
     { voice-family: "Vivien Leigh", victoria, female }

  5.8.2 Default attribute values in DTDs

   Matching takes place on attribute values in the document tree. Default
   attribute values may be defined in a DTD or elsewhere, but cannot
   always be selected by attribute selectors. Style sheets should be
   designed so that they work even if the default values are not included
   in the document tree.

   More precisely, a UA may, but is not required to, read an "external
   subset" of the DTD but is required to look for default attribute values
   in the document's "internal subset." (See [XML10] for definitions of
   these subsets.) Depending on the UA, a default attribute value defined
   in the external subset of the DTD might or might not appear in the
   document tree.

   A UA that recognizes an XML namespace [XMLNAMESPACES] may, but is not
   required to, use its knowledge of that namespace to treat default
   attribute values as if they were present in the document. (E.g., an
   XHTML UA is not required to use its built-in knowledge of the XHTML
   DTD.)

   Note that, typically, implementations choose to ignore external
   subsets.

   Example(s):

   Example:

   For example, consider an element EXAMPLE with an attribute "notation"
   that has a default value of "decimal". The DTD fragment might be
<!ATTLIST EXAMPLE notation (decimal,octal) "decimal">

   If the style sheet contains the rules
EXAMPLE[notation=decimal] { /*... default property settings ...*/ }
EXAMPLE[notation=octal]   { /*... other settings...*/ }

   the first rule might not match elements whose "notation" attribute is
   set by default, i.e., not set explicitly. To catch all cases, the
   attribute selector for the default value must be dropped:
EXAMPLE                   { /*... default property settings ...*/ }
EXAMPLE[notation=octal]   { /*... other settings...*/ }

   Here, because the selector EXAMPLE[notation=octal] is more specific
   than the type selector alone, the style declarations in the second rule
   will override those in the first for elements that have a "notation"
   attribute value of "octal". Care has to be taken that all property
   declarations that are to apply only to the default case are overridden
   in the non-default cases' style rules.

  5.8.3 Class selectors

   Working with HTML, authors may use the period (.) notation as an
   alternative to the ~= notation when representing the class attribute.
   Thus, for HTML, div.value and div[class~=value] have the same meaning.
   The attribute value must immediately follow the "period" (.). UAs may
   apply selectors using the period (.) notation in XML documents if the
   UA has namespace specific knowledge that allows it to determine which
   attribute is the "class" attribute for the respective namespace. One
   such example of namespace specific knowledge is the prose in the
   specification for a particular namespace (e.g., SVG 1.1 [SVG11]
   describes the SVG "class" attribute and how a UA should interpret it,
   and similarly MathML 3.0 [MATH30] describes the MathML "class"
   attribute.)

   Example(s):

   For example, we can assign style information to all elements with
   class~="pastoral" as follows:
*.pastoral { color: green }  /* all elements with class~=pastoral */

   or just
.pastoral { color: green }  /* all elements with class~=pastoral */

   The following assigns style only to H1 elements with class~="pastoral":
H1.pastoral { color: green }  /* H1 elements with class~=pastoral */

   Given these rules, the first H1 instance below would not have green
   text, while the second would:
<H1>Not green</H1>
<H1 class="pastoral">Very green</H1>

   To match a subset of "class" values, each value must be preceded by a
   ".".

   Example(s):

   For example, the following rule matches any P element whose "class"
   attribute has been assigned a list of space-separated values that
   includes "pastoral" and "marine":

p.marine.pastoral { color: green }

   This rule matches when class="pastoral blue aqua marine" but does not
   match for class="pastoral blue".

   Note. CSS gives so much power to the "class" attribute, that authors
   could conceivably design their own "document language" based on
   elements with almost no associated presentation (such as DIV and SPAN
   in HTML) and assigning style information through the "class" attribute.
   Authors should avoid this practice since the structural elements of a
   document language often have recognized and accepted meanings and
   author-defined classes may not.

   Note: If an element has multiple class attributes, their values must be
   concatenated with spaces between the values before searching for the
   class. As of this time the working group is not aware of any manner in
   which this situation can be reached, however, so this behavior is
   explicitly non-normative in this specification.

5.9 ID selectors

   Document languages may contain attributes that are declared to be of
   type ID. What makes attributes of type ID special is that no two such
   attributes can have the same value; whatever the document language, an
   ID attribute can be used to uniquely identify its element. In HTML all
   ID attributes are named "id"; XML applications may name ID attributes
   differently, but the same restriction applies.

   The ID attribute of a document language allows authors to assign an
   identifier to one element instance in the document tree. CSS ID
   selectors match an element instance based on its identifier. A CSS ID
   selector contains a "#" immediately followed by the ID value, which
   must be an identifier.

   Note that CSS does not specify how a UA knows the ID attribute of an
   element. The UA may, e.g., read a document's DTD, have the information
   hard-coded or ask the user.

   Example(s):

   The following ID selector matches the H1 element whose ID attribute has
   the value "chapter1":
h1#chapter1 { text-align: center }

   In the following example, the style rule matches the element that has
   the ID value "z98y". The rule will thus match for the P element:
<HEAD>
  <TITLE>Match P</TITLE>
  <STYLE type="text/css">
    *#z98y { letter-spacing: 0.3em }
  </STYLE>
</HEAD>
<BODY>
   <P id=z98y>Wide text</P>
</BODY>

   In the next example, however, the style rule will only match an H1
   element that has an ID value of "z98y". The rule will not match the P
   element in this example:
<HEAD>
  <TITLE>Match H1 only</TITLE>
  <STYLE type="text/css">
    H1#z98y { letter-spacing: 0.5em }
  </STYLE>
</HEAD>
<BODY>
   <P id=z98y>Wide text</P>
</BODY>

   ID selectors have a higher specificity than attribute selectors. For
   example, in HTML, the selector #p123 is more specific than [id=p123] in
   terms of the cascade.

   Note. In XML 1.0 [XML10], the information about which attribute
   contains an element's IDs is contained in a DTD. When parsing XML, UAs
   do not always read the DTD, and thus may not know what the ID of an
   element is. If a style sheet designer knows or suspects that this will
   be the case, he should use normal attribute selectors instead:
   [name=p371] instead of #p371. However, the cascading order of normal
   attribute selectors is different from ID selectors. It may be necessary
   to add an "!important" priority to the declarations: [name=p371]
   {color: red ! important}.

   If an element has multiple ID attributes, all of them must be treated
   as IDs for that element for the purposes of the ID selector. Such a
   situation could be reached using mixtures of xml:id [XMLID], DOM3 Core
   [DOM-LEVEL-3-CORE], XML DTDs [XML10] and namespace-specific knowledge.

5.10 Pseudo-elements and pseudo-classes

   In CSS 2.1, style is normally attached to an element based on its
   position in the document tree. This simple model is sufficient for many
   cases, but some common publishing scenarios may not be possible due to
   the structure of the document tree. For instance, in HTML 4 (see
   [HTML4]), no element refers to the first line of a paragraph, and
   therefore no simple CSS selector may refer to it.

   CSS introduces the concepts of pseudo-elements and pseudo-classes to
   permit formatting based on information that lies outside the document
   tree.
     * Pseudo-elements create abstractions about the document tree beyond
       those specified by the document language. For instance, document
       languages do not offer mechanisms to access the first letter or
       first line of an element's content. CSS pseudo-elements allow style
       sheet designers to refer to this otherwise inaccessible
       information. Pseudo-elements may also provide style sheet designers
       a way to assign style to content that does not exist in the source
       document (e.g., the :before and :after pseudo-elements give access
       to generated content).
     * Pseudo-classes classify elements on characteristics other than
       their name, attributes or content; in principle characteristics
       that cannot be deduced from the document tree. Pseudo-classes may
       be dynamic, in the sense that an element may acquire or lose a
       pseudo-class while a user interacts with the document. The
       exceptions are ':first-child', which can be deduced from the
       document tree, and ':lang()', which can be deduced from the
       document tree in some cases.

   Neither pseudo-elements nor pseudo-classes appear in the document
   source or document tree.

   Pseudo-classes are allowed anywhere in selectors while pseudo-elements
   may only be appended after the last simple selector of the selector.

   Pseudo-element and pseudo-class names are case-insensitive.

   Some pseudo-classes are mutually exclusive, while others can be applied
   simultaneously to the same element. In case of conflicting rules, the
   normal cascading order determines the outcome.

5.11 Pseudo-classes

  5.11.1 :first-child pseudo-class

   The :first-child pseudo-class matches an element that is the first
   child element of some other element.

   Example(s):

   In the following example, the selector matches any P element that is
   the first child of a DIV element. The rule suppresses indentation for
   the first paragraph of a DIV:
div > p:first-child { text-indent: 0 }

   This selector would match the P inside the DIV of the following
   fragment:
<P> The last P before the note.
<DIV class="note">
   <P> The first P inside the note.
</DIV>

   but would not match the second P in the following fragment:
<P> The last P before the note.
<DIV class="note">
   <H2>Note</H2>
   <P> The first P inside the note.
</DIV>

   Example(s):

   The following rule sets the font weight to 'bold' for any EM element
   that is some descendant of a P element that is a first child:
p:first-child em { font-weight : bold }

   Note that since anonymous boxes are not part of the document tree, they
   are not counted when calculating the first child.

   For example, the EM in:
<P>abc <EM>default</EM>

   is the first child of the P.

   The following two selectors are equivalent:
* > a:first-child   /* A is first child of any element */
a:first-child       /* Same */

  5.11.2 The link pseudo-classes: :link and :visited

   User agents commonly display unvisited links differently from
   previously visited ones. CSS provides the pseudo-classes ':link' and
   ':visited' to distinguish them:
     * The :link pseudo-class applies for links that have not yet been
       visited.
     * The :visited pseudo-class applies once the link has been visited by
       the user.

   UAs may return a visited link to the (unvisited) ':link' state at some
   point.

   The two states are mutually exclusive.

   The document language determines which elements are hyperlink source
   anchors. For example, in HTML4, the link pseudo-classes apply to A
   elements with an "href" attribute. Thus, the following two CSS 2.1
   declarations have similar effect:
a:link { color: red }
:link  { color: red }

   Example(s):

   If the following link:
<A class="external" href="http://out.side/">external link</A>

   has been visited, this rule:
a.external:visited { color: blue }

   will cause it to be blue.

   Note. It is possible for style sheet authors to abuse the :link and
   :visited pseudo-classes to determine which sites a user has visited
   without the user's consent.

   UAs may therefore treat all links as unvisited links, or implement
   other measures to preserve the user's privacy while rendering visited
   and unvisited links differently. See [P3P] for more information about
   handling privacy.

  5.11.3 The dynamic pseudo-classes: :hover, :active, and :focus

   Interactive user agents sometimes change the rendering in response to
   user actions. CSS provides three pseudo-classes for common cases:
     * The :hover pseudo-class applies while the user designates an
       element (with some pointing device), but does not activate it. For
       example, a visual user agent could apply this pseudo-class when the
       cursor (mouse pointer) hovers over a box generated by the element.
       User agents not supporting interactive media do not have to support
       this pseudo-class. Some conforming user agents supporting
       interactive media may not be able to support this pseudo-class
       (e.g., a pen device).
     * The :active pseudo-class applies while an element is being
       activated by the user. For example, between the times the user
       presses the mouse button and releases it.
     * The :focus pseudo-class applies while an element has the focus
       (accepts keyboard events or other forms of text input).

   An element may match several pseudo-classes at the same time.

   CSS does not define which elements may be in the above states, or how
   the states are entered and left. Scripting may change whether elements
   react to user events or not, and different devices and UAs may have
   different ways of pointing to, or activating elements.

   CSS 2.1 does not define if the parent of an element that is ':active'
   or ':hover' is also in that state.

   User agents are not required to reflow a currently displayed document
   due to pseudo-class transitions. For instance, a style sheet may
   specify that the 'font-size' of an :active link should be larger than
   that of an inactive link, but since this may cause letters to change
   position when the reader selects the link, a UA may ignore the
   corresponding style rule.

   Example(s):

a:link    { color: red }    /* unvisited links */
a:visited { color: blue }   /* visited links   */
a:hover   { color: yellow } /* user hovers     */
a:active  { color: lime }   /* active links    */

   Note that the A:hover must be placed after the A:link and A:visited
   rules, since otherwise the cascading rules will hide the 'color'
   property of the A:hover rule. Similarly, because A:active is placed
   after A:hover, the active color (lime) will apply when the user both
   activates and hovers over the A element.

   Example(s):

   An example of combining dynamic pseudo-classes:
a:focus { background: yellow }
a:focus:hover { background: white }

   The last selector matches A elements that are in pseudo-class :focus
   and in pseudo-class :hover.

   For information about the presentation of focus outlines, please
   consult the section on dynamic focus outlines.

   Note. In CSS1, the ':active' pseudo-class was mutually exclusive with
   ':link' and ':visited'. That is no longer the case. An element can be
   both ':visited' and ':active' (or ':link' and ':active') and the normal
   cascading rules determine which style declarations apply.

   Note. Also note that in CSS1, the ':active' pseudo-class only applied
   to links.

  5.11.4 The language pseudo-class: :lang

   If the document language specifies how the human language of an element
   is determined, it is possible to write selectors in CSS that match an
   element based on its language. For example, in HTML [HTML4], the
   language is determined by a combination of the "lang" attribute, the
   META element, and possibly by information from the protocol (such as
   HTTP headers). XML uses an attribute called xml:lang, and there may be
   other document language-specific methods for determining the language.

   The pseudo-class ':lang(C)' matches if the element is in language C.
   Whether there is a match is based solely on the identifier C being
   either equal to, or a hyphen-separated substring of, the element's
   language value, in the same way as if performed by the '|=' operator.
   The matching of C against the element's language value is performed
   case-insensitively for characters within the ASCII range. The
   identifier C does not have to be a valid language name.

   C must not be empty.

   Note: It is recommended that documents and protocols indicate language
   using codes from BCP 47 [BCP47] or its successor, and by means of
   "xml:lang" attributes in the case of XML-based documents [XML10]. See
   "FAQ: Two-letter or three-letter language codes."

   Example(s):

   The following rules set the quotation marks for an HTML document that
   is either in Canadian French or German:
html:lang(fr-ca) { quotes: '« ' ' »' }
html:lang(de) { quotes: '»' '«' '\2039' '\203A' }
:lang(fr) > Q { quotes: '« ' ' »' }
:lang(de) > Q { quotes: '»' '«' '\2039' '\203A' }

   The second pair of rules actually set the 'quotes' property on Q
   elements according to the language of its parent. This is done because
   the choice of quote marks is typically based on the language of the
   element around the quote, not the quote itself: like this piece of
   French “à l'improviste” in the middle of an English text uses the
   English quotation marks.

   Note the difference between [lang|=xx] and :lang(xx). In this HTML
   example, only the BODY matches [lang|=fr] (because it has a LANG
   attribute) but both the BODY and the P match :lang(fr) (because both
   are in French).
<body lang=fr>
  <p>Je suis Français.</p>
</body>

5.12 Pseudo-elements

   Pseudo-elements behave just like real elements in CSS with the
   exceptions described below and elsewhere.

   Note that the sections below do not define the exact rendering of
   ':first-line' and ':first-letter' in all cases. A future level of CSS
   may define them more precisely.

  5.12.1 The :first-line pseudo-element

   The :first-line pseudo-element applies special styles to the contents
   of the first formatted line of a paragraph. For instance:
p:first-line { text-transform: uppercase }

   The above rule means "change the letters of the first line of every
   paragraph to uppercase". However, the selector "P:first-line" does not
   match any real HTML element. It does match a pseudo-element that
   conforming user agents will insert at the beginning of every paragraph.

   Note that the length of the first line depends on a number of factors,
   including the width of the page, the font size, etc. Thus, an ordinary
   HTML paragraph such as:
<P>This is a somewhat long HTML
paragraph that will be broken into several
lines. The first line will be identified
by a fictional tag sequence. The other lines
will be treated as ordinary lines in the
paragraph.</P>

   the lines of which happen to be broken as follows:
THIS IS A SOMEWHAT LONG HTML PARAGRAPH THAT
will be broken into several lines. The first
line will be identified by a fictional tag
sequence. The other lines will be treated as
ordinary lines in the paragraph.

   might be "rewritten" by user agents to include the fictional tag
   sequence for :first-line. This fictional tag sequence helps to show how
   properties are inherited.
<P><P:first-line> This is a somewhat long HTML
paragraph that </P:first-line> will be broken into several
lines. The first line will be identified
by a fictional tag sequence. The other lines
will be treated as ordinary lines in the
paragraph.</P>

   If a pseudo-element breaks up a real element, the desired effect can
   often be described by a fictional tag sequence that closes and then
   re-opens the element. Thus, if we mark up the previous paragraph with a
   SPAN element:
<P><SPAN class="test"> This is a somewhat long HTML
paragraph that will be broken into several
lines.</SPAN> The first line will be identified
by a fictional tag sequence. The other lines
will be treated as ordinary lines in the
paragraph.</P>

   the user agent could simulate start and end tags for SPAN when
   inserting the fictional tag sequence for :first-line.
<P><P:first-line><SPAN class="test"> This is a
somewhat long HTML
paragraph that will </SPAN></P:first-line><SPAN class="test"> be
broken into several
lines.</SPAN> The first line will be identified
by a fictional tag sequence. The other lines
will be treated as ordinary lines in the
paragraph.</P>

   The :first-line pseudo-element can only be attached to a block
   container element.

   The "first formatted line" of an element may occur inside a block-level
   descendant in the same flow (i.e., a block-level descendant that is not
   positioned and not a float). E.g., the first line of the DIV in
   <DIV><P>This line...</P></DIV> is the first line of the P (assuming
   that both P and DIV are block-level).

   The first line of a table-cell or inline-block cannot be the first
   formatted line of an ancestor element. Thus, in <DIV><P STYLE="display:
   inline-block">Hello<BR>Goodbye</P> etcetera</DIV> the first formatted
   line of the DIV is not the line "Hello".

   Note that the first line of the P in this fragment: <p><br>First...
   does not contain any letters (assuming the default style for BR in HTML
   4). The word "First" is not on the first formatted line.

   A UA should act as if the fictional start tags of the first-line
   pseudo-elements were nested just inside the innermost enclosing
   block-level element. (Since CSS1 and CSS2 were silent on this case,
   authors should not rely on this behavior.) Here is an example. The
   fictional tag sequence for
<DIV>
  <P>First paragraph</P>
  <P>Second paragraph</P>
</DIV>

   is
<DIV>
  <P><DIV:first-line><P:first-line>First paragraph</P:first-line></DIV:first-lin
e></P>
  <P><P:first-line>Second paragraph</P:first-line></P>
</DIV>

   The :first-line pseudo-element is similar to an inline-level element,
   but with certain restrictions. The following properties apply to a
   :first-line pseudo-element: font properties, color property, background
   properties, 'word-spacing', 'letter-spacing', 'text-decoration',
   'text-transform', and 'line-height'. UAs may apply other properties as
   well.

  5.12.2 The :first-letter pseudo-element

   The :first-letter pseudo-element must select the first letter of the
   first line of a block, if it is not preceded by any other content (such
   as images or inline tables) on its line. The :first-letter
   pseudo-element may be used for "initial caps" and "drop caps", which
   are common typographical effects. This type of initial letter is
   similar to an inline-level element if its 'float' property is 'none',
   otherwise it is similar to a floated element.

   These are the properties that apply to :first-letter pseudo-elements:
   font properties, 'text-decoration', 'text-transform', 'letter-spacing',
   'word-spacing' (when appropriate), 'line-height', 'float',
   'vertical-align' (only if 'float' is 'none'), margin properties,
   padding properties, border properties, color property, background
   properties. UAs may apply other properties as well. To allow UAs to
   render a typographically correct drop cap or initial cap, the UA may
   choose a line-height, width and height based on the shape of the
   letter, unlike for normal elements. CSS3 is expected to have specific
   properties that apply to first-letter.

   This example shows a possible rendering of an initial cap. Note that
   the 'line-height' that is inherited by the first-letter pseudo-element
   is 1.1, but the UA in this example has computed the height of the first
   letter differently, so that it does not cause any unnecessary space
   between the first two lines. Also note that the fictional start tag of
   the first letter is inside the SPAN, and thus the font weight of the
   first letter is normal, not bold as the SPAN:
p { line-height: 1.1 }
p:first-letter { font-size: 3em; font-weight: normal }
span { font-weight: bold }
...
<p><span>Het hemelsche</span> gerecht heeft zich ten lange lesten<br>
Erbarremt over my en mijn benaeuwde vesten<br>
En arme burgery, en op mijn volcx gebed<br>
En dagelix geschrey de bange stad ontzet.

   Image illustrating the :first-letter pseudo-element

   The following CSS 2.1 will make a drop cap initial letter span about
   two lines:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
 <HEAD>
  <TITLE>Drop cap initial letter</TITLE>
  <STYLE type="text/css">
   P              { font-size: 12pt; line-height: 1.2 }
   P:first-letter { font-size: 200%; font-style: italic;
                    font-weight: bold; float: left }
   SPAN           { text-transform: uppercase }
  </STYLE>
 </HEAD>
 <BODY>
  <P><SPAN>The first</SPAN> few words of an article
    in The Economist.</P>
 </BODY>
</HTML>

   This example might be formatted as follows:

   Image illustrating the combined effect of the :first-letter and
   :first-line pseudo-elements    [D]

   The fictional tag sequence is:
<P>
<SPAN>
<P:first-letter>
T
</P:first-letter>he first
</SPAN>
few words of an article in the Economist.
</P>

   Note that the :first-letter pseudo-element tags abut the content (i.e.,
   the initial character), while the :first-line pseudo-element start tag
   is inserted right after the start tag of the block element.

   In order to achieve traditional drop caps formatting, user agents may
   approximate font sizes, for example to align baselines. Also, the glyph
   outline may be taken into account when formatting.

   Punctuation (i.e, characters defined in Unicode [UNICODE] in the "open"
   (Ps), "close" (Pe), "initial" (Pi). "final" (Pf) and "other" (Po)
   punctuation classes), that precedes or follows the first letter should
   be included, as in:

   Quotes that precede the first letter should be included.    [D]

   The ':first-letter' also applies if the first letter is in fact a
   digit, e.g., the "6" in "67 million dollars is a lot of money."

   The :first-letter pseudo-element applies to block container elements.

   The :first-letter pseudo-element can be used with all such elements
   that contain text, or that have a descendant in the same flow that
   contains text. A UA should act as if the fictional start tag of the
   first-letter pseudo-element is just before the first text of the
   element, even if that first text is in a descendant.

   Example(s):

   Here is an example. The fictional tag sequence for this HTML fragment:
<div>
<p>The first text.

   is:
<div>
<p><div:first-letter><p:first-letter>T</...></...>he first text.

   The first letter of a table-cell or inline-block cannot be the first
   letter of an ancestor element. Thus, in <DIV><P STYLE="display:
   inline-block">Hello<BR>Goodbye</P> etcetera</DIV> the first letter of
   the DIV is not the letter "H". In fact, the DIV does not have a first
   letter.

   The first letter must occur on the first formatted line. For example,
   in this fragment: <p><br>First... the first line does not contain any
   letters and ':first-letter' does not match anything (assuming the
   default style for BR in HTML 4). In particular, it does not match the
   "F" of "First."

   If an element is a list item ('display: list-item'), the
   ':first-letter' applies to the first letter in the principal box after
   the marker. UAs may ignore ':first-letter' on list items with
   'list-style-position: inside'. If an element has ':before' or ':after'
   content, the ':first-letter applies to the first letter of the element
   including that content.

   E.g., after the rule 'p:before {content: "Note: "}', the selector
   'p:first-letter' matches the "N" of "Note".

   Some languages may have specific rules about how to treat certain
   letter combinations. In Dutch, for example, if the letter combination
   "ij" appears at the beginning of a word, both letters should be
   considered within the :first-letter pseudo-element.

   If the letters that would form the first-letter are not in the same
   element, such as "'T" in <p>'<em>T..., the UA may create a first-letter
   pseudo-element from one of the elements, both elements, or simply not
   create a pseudo-element.

   Similarly, if the first letter(s) of the block are not at the start of
   the line (for example due to bidirectional reordering), then the UA
   need not create the pseudo-element(s).

   Example(s):

   The following example illustrates how overlapping pseudo-elements may
   interact. The first letter of each P element will be green with a font
   size of '24pt'. The rest of the first formatted line will be 'blue'
   while the rest of the paragraph will be 'red'.
p { color: red; font-size: 12pt }
p:first-letter { color: green; font-size: 200% }
p:first-line { color: blue }

<P>Some text that ends up on two lines</P>

   Assuming that a line break will occur before the word "ends", the
   fictional tag sequence for this fragment might be:
<P>
<P:first-line>
<P:first-letter>
S
</P:first-letter>ome text that
</P:first-line>
ends up on two lines
</P>

   Note that the :first-letter element is inside the :first-line element.
   Properties set on :first-line are inherited by :first-letter, but are
   overridden if the same property is set on :first-letter.

  5.12.3 The :before and :after pseudo-elements

   The ':before' and ':after' pseudo-elements can be used to insert
   generated content before or after an element's content. They are
   explained in the section on generated text.

   Example(s):

h1:before {content: counter(chapno, upper-roman) ". "}

   When the :first-letter and :first-line pseudo-elements are applied to
   an element having content generated using :before and :after, they
   apply to the first letter or line of the element including the
   generated content.

   Example(s):

p.special:before {content: "Special! "}
p.special:first-letter {color: #ffd800}

   This will render the "S" of "Special!" in gold.

            6 Assigning property values, Cascading, and Inheritance

   Contents
     * 6.1 Specified, computed, and actual values
          + 6.1.1 Specified values
          + 6.1.2 Computed values
          + 6.1.3 Used values
          + 6.1.4 Actual values
     * 6.2 Inheritance
          + 6.2.1 The 'inherit' value
     * 6.3 The @import rule
     * 6.4 The cascade
          + 6.4.1 Cascading order
          + 6.4.2 !important rules
          + 6.4.3 Calculating a selector's specificity
          + 6.4.4 Precedence of non-CSS presentational hints

6.1 Specified, computed, and actual values

   Once a user agent has parsed a document and constructed a document
   tree, it must assign, for every element in the tree, a value to every
   property that applies to the target media type.

   The final value of a property is the result of a four-step calculation:
   the value is determined through specification (the "specified value"),
   then resolved into a value that is used for inheritance (the "computed
   value"), then converted into an absolute value if necessary (the "used
   value"), and finally transformed according to the limitations of the
   local environment (the "actual value").

  6.1.1 Specified values

   User agents must first assign a specified value to each property based
   on the following mechanisms (in order of precedence):
    1. If the cascade results in a value, use it.
    2. Otherwise, if the property is inherited and the element is not the
       root of the document tree, use the computed value of the parent
       element.
    3. Otherwise use the property's initial value. The initial value of
       each property is indicated in the property's definition.

  6.1.2 Computed values

   Specified values are resolved to computed values during the cascade;
   for example URIs are made absolute and 'em' and 'ex' units are computed
   to pixel or absolute lengths. Computing a value never requires the user
   agent to render the document.

   The computed value of URIs that the UA cannot resolve to absolute URIs
   is the specified value.

   The computed value of a property is determined as specified by the
   Computed Value line in the definition of the property. See the section
   on inheritance for the definition of computed values when the specified
   value is 'inherit'.

   The computed value exists even when the property does not apply, as
   defined by the 'Applies To' line. However, some properties may define
   the computed value of a property for an element to depend on whether
   the property applies to that element.

  6.1.3 Used values

   Computed values are processed as far as possible without formatting the
   document. Some values, however, can only be determined when the
   document is being laid out. For example, if the width of an element is
   set to be a certain percentage of its containing block, the width
   cannot be determined until the width of the containing block has been
   determined. The used value is the result of taking the computed value
   and resolving any remaining dependencies into an absolute value.

  6.1.4 Actual values

   A used value is in principle the value used for rendering, but a user
   agent may not be able to make use of the value in a given environment.
   For example, a user agent may only be able to render borders with
   integer pixel widths and may therefore have to approximate the computed
   width, or the user agent may be forced to use only black and white
   shades instead of full color. The actual value is the used value after
   any approximations have been applied.

6.2 Inheritance

   Some values are inherited by the children of an element in the document
   tree, as described above. Each property defines whether it is inherited
   or not.

   Suppose there is an H1 element with an emphasizing element (EM) inside:
<H1>The headline <EM>is</EM> important!</H1>

   If no color has been assigned to the EM element, the emphasized "is"
   will inherit the color of the parent element, so if H1 has the color
   blue, the EM element will likewise be in blue.

   When inheritance occurs, elements inherit computed values. The computed
   value from the parent element becomes both the specified value and the
   computed value on the child.

   Example(s):

   For example, given the following style sheet:
body { font-size: 10pt }
h1 { font-size: 130% }

   and this document fragment:
<BODY>
  <H1>A <EM>large</EM> heading</H1>
</BODY>

   the 'font-size' property for the H1 element will have the computed
   value '13pt' (130% times 10pt, the parent's value). Since the computed
   value of 'font-size' is inherited, the EM element will have the
   computed value '13pt' as well. If the user agent does not have the 13pt
   font available, the actual value of 'font-size' for both H1 and EM
   might be, for example, '12pt'.

   Note that inheritance follows the document tree and is not intercepted
   by anonymous boxes.

  6.2.1 The 'inherit' value

   Each property may also have a cascaded value of 'inherit', which means
   that, for a given element, the property takes the same specified value
   as the property for the element's parent. The 'inherit' value can be
   used to enforce inheritance of values, and it can also be used on
   properties that are not normally inherited.

   If the 'inherit' value is set on the root element, the property is
   assigned its initial value.

   Example(s):

   In the example below, the 'color' and 'background' properties are set
   on the BODY element. On all other elements, the 'color' value will be
   inherited and the background will be transparent. If these rules are
   part of the user's style sheet, black text on a white background will
   be enforced throughout the document.
body {
  color: black !important;
  background: white !important;
}

* {
  color: inherit !important;
  background: transparent !important;
}

6.3 The @import rule

   The '@import' rule allows users to import style rules from other style
   sheets. In CSS 2.1, any @import rules must precede all other rules
   (except the @charset rule, if present). See the section on parsing for
   when user agents must ignore @import rules. The '@import' keyword must
   be followed by the URI of the style sheet to include. A string is also
   allowed; it will be interpreted as if it had url(...) around it.

   Example(s):

   The following lines are equivalent in meaning and illustrate both
   '@import' syntaxes (one with "url()" and one with a bare string):
@import "mystyle.css";
@import url("mystyle.css");

   So that user agents can avoid retrieving resources for unsupported
   media types, authors may specify media-dependent @import rules. These
   conditional imports specify comma-separated media types after the URI.

   Example(s):

   The following rules illustrate how @import rules can be made
   media-dependent:
@import url("fineprint.css") print;
@import url("bluish.css") projection, tv;

   In the absence of any media types, the import is unconditional.
   Specifying 'all' for the medium has the same effect. The import only
   takes effect if the target medium matches the media list.

   A target medium matches a media list if one of the items in the media
   list is the target medium or 'all'.

   Note that Media Queries [MEDIAQ] extends the syntax of media lists and
   the definition of matching.

   When the same style sheet is imported or linked to a document in
   multiple places, user agents must process (or act as though they do)
   each link as though the link were to a separate style sheet.

6.4 The cascade

   Style sheets may have three different origins: author, user, and user
   agent.
     * Author. The author specifies style sheets for a source document
       according to the conventions of the document language. For
       instance, in HTML, style sheets may be included in the document or
       linked externally.
     * User: The user may be able to specify style information for a
       particular document. For example, the user may specify a file that
       contains a style sheet or the user agent may provide an interface
       that generates a user style sheet (or behaves as if it did).
     * User agent: Conforming user agents must apply a default style sheet
       (or behave as if they did). A user agent's default style sheet
       should present the elements of the document language in ways that
       satisfy general presentation expectations for the document language
       (e.g., for visual browsers, the EM element in HTML is presented
       using an italic font). See A sample style sheet for HTML for a
       recommended default style sheet for HTML documents.
       Note that the user may modify system settings (e.g., system colors)
       that affect the default style sheet. However, some user agent
       implementations make it impossible to change the values in the
       default style sheet.

   Style sheets from these three origins will overlap in scope, and they
   interact according to the cascade.

   The CSS cascade assigns a weight to each style rule. When several rules
   apply, the one with the greatest weight takes precedence.

   By default, rules in author style sheets have more weight than rules in
   user style sheets. Precedence is reversed, however, for "!important"
   rules. All user and author rules have more weight than rules in the
   UA's default style sheet.

  6.4.1 Cascading order

   To find the value for an element/property combination, user agents must
   apply the following sorting order:
    1. Find all declarations that apply to the element and property in
       question, for the target media type. Declarations apply if the
       associated selector matches the element in question and the target
       medium matches the media list on all @media rules containing the
       declaration and on all links on the path through which the style
       sheet was reached.
    2. Sort according to importance (normal or important) and origin
       (author, user, or user agent). In ascending order of precedence:
         1. user agent declarations
         2. user normal declarations
         3. author normal declarations
         4. author important declarations
         5. user important declarations
    3. Sort rules with the same importance and origin by specificity of
       selector: more specific selectors will override more general ones.
       Pseudo-elements and pseudo-classes are counted as normal elements
       and classes, respectively.
    4. Finally, sort by order specified: if two declarations have the same
       weight, origin and specificity, the latter specified wins.
       Declarations in imported style sheets are considered to be before
       any declarations in the style sheet itself.

   Apart from the "!important" setting on individual declarations, this
   strategy gives author's style sheets higher weight than those of the
   reader. User agents must give the user the ability to turn off the
   influence of specific author style sheets, e.g., through a pull-down
   menu. Conformance to UAAG 1.0 checkpoint 4.14 satisfies this condition
   [UAAG10].

  6.4.2 !important rules

   CSS attempts to create a balance of power between author and user style
   sheets. By default, rules in an author's style sheet override those in
   a user's style sheet (see cascade rule 3).

   However, for balance, an "!important" declaration (the delimiter token
   "!" and keyword "important" follow the declaration) takes precedence
   over a normal declaration. Both author and user style sheets may
   contain "!important" declarations, and user "!important" rules override
   author "!important" rules. This CSS feature improves accessibility of
   documents by giving users with special requirements (large fonts, color
   combinations, etc.) control over presentation.

   Declaring a shorthand property (e.g., 'background') to be "!important"
   is equivalent to declaring all of its sub-properties to be
   "!important".

   Example(s):

   The first rule in the user's style sheet in the following example
   contains an "!important" declaration, which overrides the corresponding
   declaration in the author's style sheet. The second declaration will
   also win due to being marked "!important". However, the third rule in
   the user's style sheet is not "!important" and will therefore lose to
   the second rule in the author's style sheet (which happens to set style
   on a shorthand property). Also, the third author rule will lose to the
   second author rule since the second rule is "!important". This shows
   that "!important" declarations have a function also within author style
   sheets.
/* From the user's style sheet */
p { text-indent: 1em ! important }
p { font-style: italic ! important }
p { font-size: 18pt }

/* From the author's style sheet */
p { text-indent: 1.5em !important }
p { font: normal 12pt sans-serif !important }
p { font-size: 24pt }

  6.4.3 Calculating a selector's specificity

   A selector's specificity is calculated as follows:
     * count 1 if the declaration is from is a 'style' attribute rather
       than a rule with a selector, 0 otherwise (= a) (In HTML, values of
       an element's "style" attribute are style sheet rules. These rules
       have no selectors, so a=1, b=0, c=0, and d=0.)
     * count the number of ID attributes in the selector (= b)
     * count the number of other attributes and pseudo-classes in the
       selector (= c)
     * count the number of element names and pseudo-elements in the
       selector (= d)

   The specificity is based only on the form of the selector. In
   particular, a selector of the form "[id=p33]" is counted as an
   attribute selector (a=0, b=0, c=1, d=0), even if the id attribute is
   defined as an "ID" in the source document's DTD.

   Concatenating the four numbers a-b-c-d (in a number system with a large
   base) gives the specificity.

   Example(s):

   Some examples:
 *             {}  /* a=0 b=0 c=0 d=0 -> specificity = 0,0,0,0 */
 li            {}  /* a=0 b=0 c=0 d=1 -> specificity = 0,0,0,1 */
 li:first-line {}  /* a=0 b=0 c=0 d=2 -> specificity = 0,0,0,2 */
 ul li         {}  /* a=0 b=0 c=0 d=2 -> specificity = 0,0,0,2 */
 ul ol+li      {}  /* a=0 b=0 c=0 d=3 -> specificity = 0,0,0,3 */
 h1 + *[rel=up]{}  /* a=0 b=0 c=1 d=1 -> specificity = 0,0,1,1 */
 ul ol li.red  {}  /* a=0 b=0 c=1 d=3 -> specificity = 0,0,1,3 */
 li.red.level  {}  /* a=0 b=0 c=2 d=1 -> specificity = 0,0,2,1 */
 #x34y         {}  /* a=0 b=1 c=0 d=0 -> specificity = 0,1,0,0 */
 style=""          /* a=1 b=0 c=0 d=0 -> specificity = 1,0,0,0 */

<HEAD>
<STYLE type="text/css">
  #x97z { color: red }
</STYLE>
</HEAD>
<BODY>
<P ID=x97z style="color: green">
</BODY>

   In the above example, the color of the P element would be green. The
   declaration in the "style" attribute will override the one in the STYLE
   element because of cascading rule 3, since it has a higher specificity.

  6.4.4 Precedence of non-CSS presentational hints

   The UA may choose to honor presentational attributes in an HTML source
   document. If so, these attributes are translated to the corresponding
   CSS rules with specificity equal to 0, and are treated as if they were
   inserted at the start of the author style sheet. They may therefore be
   overridden by subsequent style sheet rules. In a transition phase, this
   policy will make it easier for stylistic attributes to coexist with
   style sheets.

   For HTML, any attribute that is not in the following list should be
   considered presentational: abbr, accept-charset, accept, accesskey,
   action, alt, archive, axis, charset, checked, cite, class, classid,
   code, codebase, codetype, colspan, coords, data, datetime, declare,
   defer, dir, disabled, enctype, for, headers, href, hreflang,
   http-equiv, id, ismap, label, lang, language, longdesc, maxlength,
   media, method, multiple, name, nohref, object, onblur, onchange,
   onclick, ondblclick, onfocus, onkeydown, onkeypress, onkeyup, onload,
   onload, onmousedown, onmousemove, onmouseout, onmouseover, onmouseup,
   onreset, onselect, onsubmit, onunload, onunload, profile, prompt,
   readonly, rel, rev, rowspan, scheme, scope, selected, shape, span, src,
   standby, start, style, summary, title, type (except on LI, OL and UL
   elements), usemap, value, valuetype, version.

   For other languages, all document language-based styling must be
   translated to the corresponding CSS and either enter the cascade at the
   user agent level or, as with HTML presentational hints, be treated as
   author level rules with a specificity of zero placed at the start of
   the author style sheet.

   Example(s):

   The following user style sheet would override the font weight of 'b'
   elements in all documents, and the color of 'font' elements with color
   attributes in XML documents. It would not affect the color of any
   'font' elements with color attributes in HTML documents:
b { font-weight: normal; }
font[color] { color: orange; }

   The following, however, would override the color of font elements in
   all documents:
font[color] { color: orange ! important; }

                                 7 Media types

   Contents
     * 7.1 Introduction to media types
     * 7.2 Specifying media-dependent style sheets
          + 7.2.1 The @media rule
     * 7.3 Recognized media types
          + 7.3.1 Media groups

7.1 Introduction to media types

   One of the most important features of style sheets is that they specify
   how a document is to be presented on different media: on the screen, on
   paper, with a speech synthesizer, with a braille device, etc.

   Certain CSS properties are only designed for certain media (e.g., the
   'page-break-before' property only applies to paged media). On occasion,
   however, style sheets for different media types may share a property,
   but require different values for that property. For example, the
   'font-size' property is useful both for screen and print media. The two
   media types are different enough to require different values for the
   common property; a document will typically need a larger font on a
   computer screen than on paper. Therefore, it is necessary to express
   that a style sheet, or a section of a style sheet, applies to certain
   media types.

7.2 Specifying media-dependent style sheets

   There are currently two ways to specify media dependencies for style
   sheets:
     * Specify the target medium from a style sheet with the @media or
       @import at-rules.
       Example(s):
@import url("fancyfonts.css") screen;
@media print {
  /* style sheet for print goes here */
}

     * Specify the target medium within the document language. For
       example, in HTML 4 ([HTML4]), the "media" attribute on the LINK
       element specifies the target media of an external style sheet:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
   <HEAD>
      <TITLE>Link to a target medium</TITLE>
      <LINK REL="stylesheet" TYPE="text/css"
         MEDIA="print, handheld" HREF="foo.css">
   </HEAD>
   <BODY>
      <P>The body...
   </BODY>
</HTML>

   The @import rule is defined in the chapter on the cascade.

  7.2.1 The @media rule

   An @media rule specifies the target media types (separated by commas)
   of a set of statements (delimited by curly braces). Invalid statements
   must be ignored per 4.1.7 "Rule sets, declaration blocks, and
   selectors" and 4.2 "Rules for handling parsing errors." The @media
   construct allows style sheet rules for various media in the same style
   sheet:
  @media print {
    body { font-size: 10pt }
  }
  @media screen {
    body { font-size: 13px }
  }
  @media screen, print {
    body { line-height: 1.2 }
  }

   Style rules outside of @media rules apply to all media types that the
   style sheet applies to. At-rules inside @media are invalid in CSS2.1.

7.3 Recognized media types

   The names chosen for CSS media types reflect target devices for which
   the relevant properties make sense. In the following list of CSS media
   types the names of media types are normative, but the descriptions are
   informative. Likewise, the "Media" field in the description of each
   property is informative.

   all
          Suitable for all devices.

   braille
          Intended for braille tactile feedback devices.

   embossed
          Intended for paged braille printers.

   handheld
          Intended for handheld devices (typically small screen, limited
          bandwidth).

   print
          Intended for paged material and for documents viewed on screen
          in print preview mode. Please consult the section on paged media
          for information about formatting issues that are specific to
          paged media.

   projection
          Intended for projected presentations, for example projectors.
          Please consult the section on paged media for information about
          formatting issues that are specific to paged media.

   screen
          Intended primarily for color computer screens.

   speech
          Intended for speech synthesizers. Note: CSS2 had a similar media
          type called 'aural' for this purpose. See the appendix on aural
          style sheets for details.

   tty
          Intended for media using a fixed-pitch character grid (such as
          teletypes, terminals, or portable devices with limited display
          capabilities). Authors should not use pixel units with the "tty"
          media type.

   tv
          Intended for television-type devices (low resolution, color,
          limited-scrollability screens, sound available).

   Media type names are case-insensitive.

   Media types are mutually exclusive in the sense that a user agent can
   only support one media type when rendering a document. However, user
   agents may use different media types on different canvases. For
   example, a document may (simultaneously) be shown in 'screen' mode on
   one canvas and 'print' mode on another canvas.

   Note that a multimodal media type is still only one media type. The
   'tv' media type, for example, is a multimodal media type that renders
   both visually and aurally to a single canvas.

   @media and @import rules with unknown media types (that are nonetheless
   valid identifiers) are treated as if the unknown media types are not
   present. If an @media/@import rule contains a malformed media type (not
   an identifier) then the statement is invalid.

   Note: Media Queries supercedes this error handling.

   Example(s):

   For example, in the following snippet, the rule on the P element
   applies in 'screen' mode (even though the '3D' media type is not
   known).
@media screen, 3D {
  P { color: green; }
}

   Note. Future updates of CSS may extend the list of media types. Authors
   should not rely on media type names that are not yet defined by a CSS
   specification.

  7.3.1 Media groups

   This section is informative, not normative.

   Each CSS property definition specifies which media types the property
   applies to. Since properties generally apply to several media types,
   the "Applies to media" section of each property definition lists media
   groups rather than individual media types. Each property applies to all
   media types in the media groups listed in its definition.

   CSS 2.1 defines the following media groups:
     * continuous or paged.
     * visual, audio, speech, or tactile.
     * grid (for character grid devices), or bitmap.
     * interactive (for devices that allow user interaction), or static
       (for those that do not).
     * all (includes all media types)

   The following table shows the relationships between media groups and
   media types:

   CAPTION: Relationship between media groups and media types

   Media Types Media Groups
     continuous/paged visual/audio/speech/tactile grid/bitmap
   interactive/static
   braille continuous tactile grid both
   embossed paged tactile grid static
   handheld both visual, audio, speech both both
   print paged visual bitmap static
   projection paged visual bitmap interactive
   screen continuous visual, audio bitmap both
   speech continuous speech N/A both
   tty continuous visual grid both
   tv both visual, audio bitmap both

                                  8 Box model

   Contents
     * 8.1 Box dimensions
     * 8.2 Example of margins, padding, and borders
     * 8.3 Margin properties: 'margin-top', 'margin-right',
       'margin-bottom', 'margin-left', and 'margin'
          + 8.3.1 Collapsing margins
     * 8.4 Padding properties: 'padding-top', 'padding-right',
       'padding-bottom', 'padding-left', and 'padding'
     * 8.5 Border properties
          + 8.5.1 Border width: 'border-top-width', 'border-right-width',
            'border-bottom-width', 'border-left-width', and 'border-width'
          + 8.5.2 Border color: 'border-top-color', 'border-right-color',
            'border-bottom-color', 'border-left-color', and 'border-color'
          + 8.5.3 Border style: 'border-top-style', 'border-right-style',
            'border-bottom-style', 'border-left-style', and 'border-style'
          + 8.5.4 Border shorthand properties: 'border-top',
            'border-right', 'border-bottom', 'border-left', and 'border'
     * 8.6 The box model for inline elements in bidirectional context

   The CSS box model describes the rectangular boxes that are generated
   for elements in the document tree and laid out according to the visual
   formatting model.

8.1 Box dimensions

   Each box has a content area (e.g., text, an image, etc.) and optional
   surrounding padding, border, and margin areas; the size of each area is
   specified by properties defined below. The following diagram shows how
   these areas relate and the terminology used to refer to pieces of
   margin, border, and padding:

   Image illustrating the relationship between content, padding, borders,
   and margins.    [D]

   The margin, border, and padding can be broken down into top, right,
   bottom, and left segments (e.g., in the diagram, "LM" for left margin,
   "RP" for right padding, "TB" for top border, etc.).

   The perimeter of each of the four areas (content, padding, border, and
   margin) is called an "edge", so each box has four edges:

   content edge or inner edge
          The content edge surrounds the rectangle given by the width and
          height of the box, which often depend on the element's rendered
          content. The four content edges define the box's content box.

   padding edge
          The padding edge surrounds the box padding. If the padding has 0
          width, the padding edge is the same as the content edge. The
          four padding edges define the box's padding box.

   border edge
          The border edge surrounds the box's border. If the border has 0
          width, the border edge is the same as the padding edge. The four
          border edges define the box's border box.

   margin edge or outer edge
          The margin edge surrounds the box margin. If the margin has 0
          width, the margin edge is the same as the border edge. The four
          margin edges define the box's margin box.

   Each edge may be broken down into a top, right, bottom, and left edge.

   The dimensions of the content area of a box — the content width and
   content height — depend on several factors: whether the element
   generating the box has the 'width' or 'height' property set, whether
   the box contains text or other boxes, whether the box is a table, etc.
   Box widths and heights are discussed in the chapter on visual
   formatting model details.

   The background style of the content, padding, and border areas of a box
   is specified by the 'background' property of the generating element.
   Margin backgrounds are always transparent.

8.2 Example of margins, padding, and borders

   This example illustrates how margins, padding, and borders interact.
   The example HTML document:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
    <TITLE>Examples of margins, padding, and borders</TITLE>
    <STYLE type="text/css">
      UL {
        background: yellow;
        margin: 12px 12px 12px 12px;
        padding: 3px 3px 3px 3px;
                                     /* No borders set */
      }
      LI {
        color: white;                /* text color is white */
        background: blue;            /* Content, padding will be blue */
        margin: 12px 12px 12px 12px;
        padding: 12px 0px 12px 12px; /* Note 0px padding right */
        list-style: none             /* no glyphs before a list item */
                                     /* No borders set */
      }
      LI.withborder {
        border-style: dashed;
        border-width: medium;        /* sets border width on all sides */
        border-color: lime;
      }
    </STYLE>
  </HEAD>
  <BODY>
    <UL>
      <LI>First element of list
      <LI class="withborder">Second element of list is
           a bit longer to illustrate wrapping.
    </UL>
  </BODY>
</HTML>

   results in a document tree with (among other relationships) a UL
   element that has two LI children.

   The first of the following diagrams illustrates what this example would
   produce. The second illustrates the relationship between the margins,
   padding, and borders of the UL elements and those of its children LI
   elements. (Image is not to scale.)

   Image illustrating how parent and child margins, borders, and padding
   relate.    [D]

   Note that:
     * The content width for each LI box is calculated top-down; the
       containing block for each LI box is established by the UL element.
     * The margin box height of each LI box depends on its content height,
       plus top and bottom padding, borders, and margins. Note that
       vertical margins between the LI boxes collapse.
     * The right padding of the LI boxes has been set to zero width (the
       'padding' property). The effect is apparent in the second
       illustration.
     * The margins of the LI boxes are transparent — margins are always
       transparent — so the background color (yellow) of the UL padding
       and content areas shines through them.
     * The second LI element specifies a dashed border (the 'border-style'
       property).

8.3 Margin properties: 'margin-top', 'margin-right', 'margin-bottom',
'margin-left', and 'margin'

   Margin properties specify the width of the margin area of a box. The
   'margin' shorthand property sets the margin for all four sides while
   the other margin properties only set their respective side. These
   properties apply to all elements, but vertical margins will not have
   any effect on non-replaced inline elements.

   The properties defined in this section refer to the <margin-width>
   value type, which may take one of the following values:

   <length>
          Specifies a fixed width.

   <percentage>
          The percentage is calculated with respect to the width of the
          generated box's containing block. Note that this is true for
          'margin-top' and 'margin-bottom' as well. If the containing
          block's width depends on this element, then the resulting layout
          is undefined in CSS 2.1.

   auto
          See the section on calculating widths and margins for behavior.

   Negative values for margin properties are allowed, but there may be
   implementation-specific limits.

   'margin-top', 'margin-bottom'

         Value:            <margin-width> | inherit
         Initial:          0
         Applies to:       all elements except elements with table display types
                           other than table-caption, table and inline-table
         Inherited:        no
         Percentages:      refer to width of containing block
         Media:            visual
         Computed value:   the percentage as specified or the absolute length

   These properties have no effect on non-replaced inline elements.

   'margin-right', 'margin-left'

         Value:            <margin-width> | inherit
         Initial:          0
         Applies to:       all elements except elements with table display types
                           other than table-caption, table and inline-table
         Inherited:        no
         Percentages:      refer to width of containing block
         Media:            visual
         Computed value:   the percentage as specified or the absolute length

   These properties set the top, right, bottom, and left margin of a box.

   Example(s):

h1 { margin-top: 2em }

   'margin'

         Value:            <margin-width>{1,4} | inherit
         Initial:          see individual properties
         Applies to:       all elements except elements with table display types
                           other than table-caption, table and inline-table
         Inherited:        no
         Percentages:      refer to width of containing block
         Media:            visual
         Computed value:   see individual properties

   The 'margin' property is a shorthand property for setting 'margin-top',
   'margin-right', 'margin-bottom', and 'margin-left' at the same place in
   the style sheet.

   If there is only one component value, it applies to all sides. If there
   are two values, the top and bottom margins are set to the first value
   and the right and left margins are set to the second. If there are
   three values, the top is set to the first value, the left and right are
   set to the second, and the bottom is set to the third. If there are
   four values, they apply to the top, right, bottom, and left,
   respectively.

   Example(s):

body { margin: 2em }         /* all margins set to 2em */
body { margin: 1em 2em }     /* top & bottom = 1em, right & left = 2em */
body { margin: 1em 2em 3em } /* top=1em, right=2em, bottom=3em, left=2em */

   The last rule of the example above is equivalent to the example below:
body {
  margin-top: 1em;
  margin-right: 2em;
  margin-bottom: 3em;
  margin-left: 2em;        /* copied from opposite side (right) */
}

  8.3.1 Collapsing margins

   In CSS, the adjoining margins of two or more boxes (which might or
   might not be siblings) can combine to form a single margin. Margins
   that combine this way are said to collapse, and the resulting combined
   margin is called a collapsed margin.

   Adjoining vertical margins collapse, except:
     * Margins of the root element's box do not collapse.
     * If the top and bottom margins of an element with clearance are
       adjoining, its margins collapse with the adjoining margins of
       following siblings but that resulting margin does not collapse with
       the bottom margin of the parent block.

   Horizontal margins never collapse.

   Two margins are adjoining if and only if:
     * both belong to in-flow block-level boxes that participate in the
       same block formatting context
     * no line boxes, no clearance, no padding and no border separate them
       (Note that certain zero-height line boxes (see 9.4.2) are ignored
       for this purpose.)
     * both belong to vertically-adjacent box edges, i.e. form one of the
       following pairs:
          + top margin of a box and top margin of its first in-flow child
          + bottom margin of box and top margin of its next in-flow
            following sibling
          + bottom margin of a last in-flow child and bottom margin of its
            parent if the parent has 'auto' computed height
          + top and bottom margins of a box that does not establish a new
            block formatting context and that has zero computed
            'min-height', zero or 'auto' computed 'height', and no in-flow
            children

   A collapsed margin is considered adjoining to another margin if any of
   its component margins is adjoining to that margin.

   Note. Adjoining margins can be generated by elements that are not
   related as siblings or ancestors.

   Note the above rules imply that:
     * Margins between a floated box and any other box do not collapse
       (not even between a float and its in-flow children).
     * Margins of elements that establish new block formatting contexts
       (such as floats and elements with 'overflow' other than 'visible')
       do not collapse with their in-flow children.
     * Margins of absolutely positioned boxes do not collapse (not even
       with their in-flow children).
     * Margins of inline-block boxes do not collapse (not even with their
       in-flow children).
     * The bottom margin of an in-flow block-level element always
       collapses with the top margin of its next in-flow block-level
       sibling, unless that sibling has clearance.
     * The top margin of an in-flow block element collapses with its first
       in-flow block-level child's top margin if the element has no top
       border, no top padding, and the child has no clearance.
     * The bottom margin of an in-flow block box with a 'height' of 'auto'
       and a 'min-height' of zero collapses with its last in-flow
       block-level child's bottom margin if the box has no bottom padding
       and no bottom border and the child's bottom margin does not
       collapse with a top margin that has clearance.
     * A box's own margins collapse if the 'min-height' property is zero,
       and it has neither top or bottom borders nor top or bottom padding,
       and it has a 'height' of either 0 or 'auto', and it does not
       contain a line box, and all of its in-flow children's margins (if
       any) collapse.

   When two or more margins collapse, the resulting margin width is the
   maximum of the collapsing margins' widths. In the case of negative
   margins, the maximum of the absolute values of the negative adjoining
   margins is deducted from the maximum of the positive adjoining margins.
   If there are no positive margins, the maximum of the absolute values of
   the adjoining margins is deducted from zero.

   If the top and bottom margins of a box are adjoining, then it is
   possible for margins to collapse through it. In this case, the position
   of the element depends on its relationship with the other elements
   whose margins are being collapsed.
     * If the element's margins are collapsed with its parent's top
       margin, the top border edge of the box is defined to be the same as
       the parent's.
     * Otherwise, either the element's parent is not taking part in the
       margin collapsing, or only the parent's bottom margin is involved.
       The position of the element's top border edge is the same as it
       would have been if the element had a non-zero bottom border.

   Note that the positions of elements that have been collapsed through
   have no effect on the positions of the other elements with whose
   margins they are being collapsed; the top border edge position is only
   required for laying out descendants of these elements.

8.4 Padding properties: 'padding-top', 'padding-right', 'padding-bottom',
'padding-left', and 'padding'

   The padding properties specify the width of the padding area of a box.
   The 'padding' shorthand property sets the padding for all four sides
   while the other padding properties only set their respective side.

   The properties defined in this section refer to the <padding-width>
   value type, which may take one of the following values:

   <length>
          Specifies a fixed width.

   <percentage>
          The percentage is calculated with respect to the width of the
          generated box's containing block, even for 'padding-top' and
          'padding-bottom'. If the containing block's width depends on
          this element, then the resulting layout is undefined in CSS 2.1.

   Unlike margin properties, values for padding values cannot be negative.
   Like margin properties, percentage values for padding properties refer
   to the width of the generated box's containing block.

   'padding-top', 'padding-right', 'padding-bottom', 'padding-left'

   Value:   <padding-width> | inherit
   Initial:   0
   Applies to:   all elements except table-row-group, table-header-group,
   table-footer-group, table-row, table-column-group and table-column
   Inherited:   no
   Percentages:   refer to width of containing block
   Media:   visual
   Computed value:   the percentage as specified or the absolute length

   These properties set the top, right, bottom, and left padding of a box.

   Example(s):

blockquote { padding-top: 0.3em }

   'padding'

   Value:   <padding-width>{1,4} | inherit
   Initial:   see individual properties
   Applies to:   all elements except table-row-group, table-header-group,
   table-footer-group, table-row, table-column-group and table-column
   Inherited:   no
   Percentages:   refer to width of containing block
   Media:   visual
   Computed value:   see individual properties

   The 'padding' property is a shorthand property for setting
   'padding-top', 'padding-right', 'padding-bottom', and 'padding-left' at
   the same place in the style sheet.

   If there is only one component value, it applies to all sides. If there
   are two values, the top and bottom paddings are set to the first value
   and the right and left paddings are set to the second. If there are
   three values, the top is set to the first value, the left and right are
   set to the second, and the bottom is set to the third. If there are
   four values, they apply to the top, right, bottom, and left,
   respectively.

   The surface color or image of the padding area is specified via the
   'background' property:

   Example(s):

h1 {
  background: white;
  padding: 1em 2em;
}

   The example above specifies a '1em' vertical padding ('padding-top' and
   'padding-bottom') and a '2em' horizontal padding ('padding-right' and
   'padding-left'). The 'em' unit is relative to the element's font size:
   '1em' is equal to the size of the font in use.

8.5 Border properties

   The border properties specify the width, color, and style of the border
   area of a box. These properties apply to all elements.

   Note. Notably for HTML, user agents may render borders for certain user
   interface elements (e.g., buttons, menus, etc.) differently than for
   "ordinary" elements.

  8.5.1 Border width: 'border-top-width', 'border-right-width',
  'border-bottom-width', 'border-left-width', and 'border-width'

   The border width properties specify the width of the border area. The
   properties defined in this section refer to the <border-width> value
   type, which may take one of the following values:

   thin
          A thin border.

   medium
          A medium border.

   thick
          A thick border.

   <length>
          The border's thickness has an explicit value. Explicit border
          widths cannot be negative.

   The interpretation of the first three values depends on the user agent.
   The following relationships must hold, however:

   'thin' <='medium' <= 'thick'.

   Furthermore, these widths must be constant throughout a document.

   'border-top-width', 'border-right-width', 'border-bottom-width',
          'border-left-width'

         Value:            <border-width> | inherit
         Initial:          medium
         Applies to:       all elements
         Inherited:        no
         Percentages:      N/A
         Media:            visual
         Computed value:   absolute length; '0' if the border style is 'none' or
                           'hidden'

   These properties set the width of the top, right, bottom, and left
   border of a box.

   'border-width'

          Value:            <border-width>{1,4} | inherit
          Initial:          see individual properties
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   see individual properties

   This property is a shorthand property for setting 'border-top-width',
   'border-right-width', 'border-bottom-width', and 'border-left-width' at
   the same place in the style sheet.

   If there is only one component value, it applies to all sides. If there
   are two values, the top and bottom borders are set to the first value
   and the right and left are set to the second. If there are three
   values, the top is set to the first value, the left and right are set
   to the second, and the bottom is set to the third. If there are four
   values, they apply to the top, right, bottom, and left, respectively.

   Example(s):

   In the examples below, the comments indicate the resulting widths of
   the top, right, bottom, and left borders:
h1 { border-width: thin }                   /* thin thin thin thin */
h1 { border-width: thin thick }             /* thin thick thin thick */
h1 { border-width: thin thick medium }      /* thin thick medium thick */

  8.5.2 Border color: 'border-top-color', 'border-right-color',
  'border-bottom-color', 'border-left-color', and 'border-color'

   The border color properties specify the color of a box's border.

   'border-top-color', 'border-right-color', 'border-bottom-color',
          'border-left-color'

          Value:            <color> | transparent | inherit
          Initial:          the value of the 'color' property
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   when taken from the 'color' property, the computed
                            value of 'color'; otherwise, as specified

   'border-color'

          Value:            [ <color> | transparent ]{1,4} | inherit
          Initial:          see individual properties
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   see individual properties

   The 'border-color' property sets the color of the four borders. Values
   have the following meanings:

   <color>
          Specifies a color value.

   transparent
          The border is transparent (though it may have width).

   The 'border-color' property can have from one to four component values,
   and the values are set on the different sides as for 'border-width'.

   If an element's border color is not specified with a border property,
   user agents must use the value of the element's 'color' property as the
   computed value for the border color.

   Example(s):

   In this example, the border will be a solid black line.
p {
  color: black;
  background: white;
  border: solid;
}

  8.5.3 Border style: 'border-top-style', 'border-right-style',
  'border-bottom-style', 'border-left-style', and 'border-style'

   The border style properties specify the line style of a box's border
   (solid, double, dashed, etc.). The properties defined in this section
   refer to the <border-style> value type, which may take one of the
   following values:

   none
          No border; the computed border width is zero.

   hidden
          Same as 'none', except in terms of border conflict resolution
          for table elements.

   dotted
          The border is a series of dots.

   dashed
          The border is a series of short line segments.

   solid
          The border is a single line segment.

   double
          The border is two solid lines. The sum of the two lines and the
          space between them equals the value of 'border-width'.

   groove
          The border looks as though it were carved into the canvas.

   ridge
          The opposite of 'groove': the border looks as though it were
          coming out of the canvas.

   inset
          The border makes the box look as though it were embedded in the
          canvas.

   outset
          The opposite of 'inset': the border makes the box look as though
          it were coming out of the canvas.

   All borders are drawn on top of the box's background. The color of
   borders drawn for values of 'groove', 'ridge', 'inset', and 'outset'
   depends on the element's border color properties, but UAs may choose
   their own algorithm to calculate the actual colors used. For instance,
   if the 'border-color' has the value 'silver', then a UA could use a
   gradient of colors from white to dark gray to indicate a sloping
   border.

   'border-top-style', 'border-right-style', 'border-bottom-style',
          'border-left-style'

          Value:            <border-style> | inherit
          Initial:          none
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   'border-style'

          Value:            <border-style>{1,4} | inherit
          Initial:          see individual properties
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   see individual properties

   The 'border-style' property sets the style of the four borders. It can
   have from one to four component values, and the values are set on the
   different sides as for 'border-width' above.

   Example(s):

#xy34 { border-style: solid dotted }

   In the above example, the horizontal borders will be 'solid' and the
   vertical borders will be 'dotted'.

   Since the initial value of the border styles is 'none', no borders will
   be visible unless the border style is set.

  8.5.4 Border shorthand properties: 'border-top', 'border-right',
  'border-bottom', 'border-left', and 'border'

   'border-top', 'border-right', 'border-bottom', 'border-left'

Value:            [ <border-width> || <border-style> || <'border-top-color'> ] |
                  inherit
Initial:          see individual properties
Applies to:       all elements
Inherited:        no
Percentages:      N/A
Media:            visual
Computed value:   see individual properties

   This is a shorthand property for setting the width, style, and color of
   the top, right, bottom, and left border of a box.

   Example(s):

h1 { border-bottom: thick solid red }

   The above rule will set the width, style, and color of the border below
   the H1 element. Omitted values are set to their initial values. Since
   the following rule does not specify a border color, the border will
   have the color specified by the 'color' property:
H1 { border-bottom: thick solid }

   'border'

Value:            [ <border-width> || <border-style> || <'border-top-color'> ] |
                  inherit
Initial:          see individual properties
Applies to:       all elements
Inherited:        no
Percentages:      N/A
Media:            visual
Computed value:   see individual properties

   The 'border' property is a shorthand property for setting the same
   width, color, and style for all four borders of a box. Unlike the
   shorthand 'margin' and 'padding' properties, the 'border' property
   cannot set different values on the four borders. To do so, one or more
   of the other border properties must be used.

   Example(s):

   For example, the first rule below is equivalent to the set of four
   rules shown after it:
p { border: solid red }
p {
  border-top: solid red;
  border-right: solid red;
  border-bottom: solid red;
  border-left: solid red
}

   Since, to some extent, the properties have overlapping functionality,
   the order in which the rules are specified is important.

   Example(s):

   Consider this example:
blockquote {
  border: solid red;
  border-left: double;
  color: black;
}

   In the above example, the color of the left border is black, while the
   other borders are red. This is due to 'border-left' setting the width,
   style, and color. Since the color value is not given by the
   'border-left' property, it will be taken from the 'color' property. The
   fact that the 'color' property is set after the 'border-left' property
   is not relevant.

8.6 The box model for inline elements in bidirectional context

   For each line box, UAs must take the inline boxes generated for each
   element and render the margins, borders and padding in visual order
   (not logical order).

   When the element's 'direction' property is 'ltr', the left-most
   generated box of the first line box in which the element appears has
   the left margin, left border and left padding, and the right-most
   generated box of the last line box in which the element appears has the
   right padding, right border and right margin.

   When the element's 'direction' property is 'rtl', the right-most
   generated box of the first line box in which the element appears has
   the right padding, right border and right margin, and the left-most
   generated box of the last line box in which the element appears has the
   left margin, left border and left padding.

                           9 Visual formatting model

   Contents
     * 9.1 Introduction to the visual formatting model
          + 9.1.1 The viewport
          + 9.1.2 Containing blocks
     * 9.2 Controlling box generation
          + 9.2.1 Block-level elements and block boxes
               o 9.2.1.1 Anonymous block boxes
          + 9.2.2 Inline-level elements and inline boxes
               o 9.2.2.1 Anonymous inline boxes
          + 9.2.3 Run-in boxes
          + 9.2.4 The 'display' property
     * 9.3 Positioning schemes
          + 9.3.1 Choosing a positioning scheme: 'position' property
          + 9.3.2 Box offsets: 'top', 'right', 'bottom', 'left'
     * 9.4 Normal flow
          + 9.4.1 Block formatting contexts
          + 9.4.2 Inline formatting contexts
          + 9.4.3 Relative positioning
     * 9.5 Floats
          + 9.5.1 Positioning the float: the 'float' property
          + 9.5.2 Controlling flow next to floats: the 'clear' property
     * 9.6 Absolute positioning
          + 9.6.1 Fixed positioning
     * 9.7 Relationships between 'display', 'position', and 'float'
     * 9.8 Comparison of normal flow, floats, and absolute positioning
          + 9.8.1 Normal flow
          + 9.8.2 Relative positioning
          + 9.8.3 Floating a box
          + 9.8.4 Absolute positioning
     * 9.9 Layered presentation
          + 9.9.1 Specifying the stack level: the 'z-index' property
     * 9.10 Text direction: the 'direction' and 'unicode-bidi' properties

9.1 Introduction to the visual formatting model

   This chapter and the next describe the visual formatting model: how
   user agents process the document tree for visual media.

   In the visual formatting model, each element in the document tree
   generates zero or more boxes according to the box model. The layout of
   these boxes is governed by:
     * box dimensions and type.
     * positioning scheme (normal flow, float, and absolute positioning).
     * relationships between elements in the document tree.
     * external information (e.g., viewport size, intrinsic dimensions of
       images, etc.).

   The properties defined in this chapter and the next apply to both
   continuous media and paged media. However, the meanings of the margin
   properties vary when applied to paged media (see the page model for
   details).

   The visual formatting model does not specify all aspects of formatting
   (e.g., it does not specify a letter-spacing algorithm). Conforming user
   agents may behave differently for those formatting issues not covered
   by this specification.

  9.1.1 The viewport

   User agents for continuous media generally offer users a viewport (a
   window or other viewing area on the screen) through which users consult
   a document. User agents may change the document's layout when the
   viewport is resized (see the initial containing block).

   When the viewport is smaller than the area of the canvas on which the
   document is rendered, the user agent should offer a scrolling
   mechanism. There is at most one viewport per canvas, but user agents
   may render to more than one canvas (i.e., provide different views of
   the same document).

  9.1.2 Containing blocks

   In CSS 2.1, many box positions and sizes are calculated with respect to
   the edges of a rectangular box called a containing block. In general,
   generated boxes act as containing blocks for descendant boxes; we say
   that a box "establishes" the containing block for its descendants. The
   phrase "a box's containing block" means "the containing block in which
   the box lives," not the one it generates.

   Each box is given a position with respect to its containing block, but
   it is not confined by this containing block; it may overflow.

   The details of how a containing block's dimensions are calculated are
   described in the next chapter.

9.2 Controlling box generation

   The following sections describe the types of boxes that may be
   generated in CSS 2.1. A box's type affects, in part, its behavior in
   the visual formatting model. The 'display' property, described below,
   specifies a box's type.

  9.2.1 Block-level elements and block boxes

   Block-level elements are those elements of the source document that are
   formatted visually as blocks (e.g., paragraphs). The following values
   of the 'display' property make an element block-level: 'block',
   'list-item', and 'table'.

   Block-level boxes are boxes that participate in a block formatting
   context. Each block-level element generates a principal block-level box
   that contains descendant boxes and generated content and is also the
   box involved in any positioning scheme. Some block-level elements may
   generate additional boxes in addition to the principal box: 'list-item'
   elements. These additional boxes are placed with respect to the
   principal box.

   Except for table boxes, which are described in a later chapter, and
   replaced elements, a block-level box is also a block container box. A
   block container box either contains only block-level boxes or
   establishes an inline formatting context and thus contains only
   inline-level boxes. Not all block container boxes are block-level
   boxes: non-replaced inline blocks and non-replaced table cells are
   block containers but not block-level boxes. Block-level boxes that are
   also block containers are called block boxes.

   The three terms "block-level box," "block container box," and "block
   box" are sometimes abbreviated as "block" where unambiguous.

    9.2.1.1 Anonymous block boxes

   In a document like this:
<DIV>
  Some text
  <P>More text
</DIV>

   (and assuming the DIV and the P both have 'display: block'), the DIV
   appears to have both inline content and block content. To make it
   easier to define the formatting, we assume that there is an anonymous
   block box around "Some text".

   diagram showing the three boxes for the example above    [D]

   Diagram showing the three boxes, of which one is anonymous, for the
   example above.

   In other words: if a block container box (such as that generated for
   the DIV above) has a block-level box inside it (such as the P above),
   then we force it to have only block-level boxes inside it.

   When an inline box contains an in-flow block-level box, the inline box
   (and its inline ancestors within the same line box) are broken around
   the block-level box (and any block-level siblings that are consecutive
   or separated only by collapsible whitespace and/or out-of-flow
   elements), splitting the inline box into two boxes (even if either side
   is empty), one on each side of the block-level box(es). The line boxes
   before the break and after the break are enclosed in anonymous block
   boxes, and the block-level box becomes a sibling of those anonymous
   boxes. When such an inline box is affected by relative positioning, any
   resulting translation also affects the block-level box contained in the
   inline box.

   Example(s):

   This model would apply in the following example if the following rules:
p    { display: inline }
span { display: block }

   were used with this HTML document:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HEAD>
<TITLE>Anonymous text interrupted by a block</TITLE>
</HEAD>
<BODY>
<P>
This is anonymous text before the SPAN.
<SPAN>This is the content of SPAN.</SPAN>
This is anonymous text after the SPAN.
</P>
</BODY>

   The P element contains a chunk (C1) of anonymous text followed by a
   block-level element followed by another chunk (C2) of anonymous text.
   The resulting boxes would be a block box representing the BODY,
   containing an anonymous block box around C1, the SPAN block box, and
   another anonymous block box around C2.

   The properties of anonymous boxes are inherited from the enclosing
   non-anonymous box (e.g., in the example just below the subsection
   heading "Anonymous block boxes", the one for DIV). Non-inherited
   properties have their initial value. For example, the font of the
   anonymous box is inherited from the DIV, but the margins will be 0.

   Properties set on elements that cause anonymous block boxes to be
   generated still apply to the boxes and content of that element. For
   example, if a border had been set on the P element in the above
   example, the border would be drawn around C1 (open at the end of the
   line) and C2 (open at the start of the line).

   Some user agents have implemented borders on inlines containing blocks
   in other ways, e.g., by wrapping such nested blocks inside "anonymous
   line boxes" and thus drawing inline borders around such boxes. As CSS1
   and CSS2 did not define this behavior, CSS1-only and CSS2-only user
   agents may implement this alternative model and still claim conformance
   to this part of CSS 2.1. This does not apply to UAs developed after
   this specification was released.

   Anonymous block boxes are ignored when resolving percentage values that
   would refer to it: the closest non-anonymous ancestor box is used
   instead. For example, if the child of the anonymous block box inside
   the DIV above needs to know the height of its containing block to
   resolve a percentage height, then it will use the height of the
   containing block formed by the DIV, not of the anonymous block box.

  9.2.2 Inline-level elements and inline boxes

   Inline-level elements are those elements of the source document that do
   not form new blocks of content; the content is distributed in lines
   (e.g., emphasized pieces of text within a paragraph, inline images,
   etc.). The following values of the 'display' property make an element
   inline-level: 'inline', 'inline-table', and 'inline-block'.
   Inline-level elements generate inline-level boxes, which are boxes that
   participate in an inline formatting context.

   An inline box is one that is both inline-level and whose contents
   participate in its containing inline formatting context. A non-replaced
   element with a 'display' value of 'inline' generates an inline box.
   Inline-level boxes that are not inline boxes (such as replaced
   inline-level elements, inline-block elements, and inline-table
   elements) are called atomic inline-level boxes because they participate
   in their inline formatting context as a single opaque box.

    9.2.2.1 Anonymous inline boxes

   Any text that is directly contained inside a block container element
   (not inside an inline element) must be treated as an anonymous inline
   element.

   In a document with HTML markup like this:

<p>Some <em>emphasized</em> text</p>

   the <p> generates a block box, with several inline boxes inside it. The
   box for "emphasized" is an inline box generated by an inline element
   (<em>), but the other boxes ("Some" and "text") are inline boxes
   generated by a block-level element (<p>). The latter are called
   anonymous inline boxes, because they do not have an associated
   inline-level element.

   Such anonymous inline boxes inherit inheritable properties from their
   block parent box. Non-inherited properties have their initial value. In
   the example, the color of the anonymous inline boxes is inherited from
   the P, but the background is transparent.

   White space content that would subsequently be collapsed away according
   to the 'white-space' property does not generate any anonymous inline
   boxes.

   If it is clear from the context which type of anonymous box is meant,
   both anonymous inline boxes and anonymous block boxes are simply called
   anonymous boxes in this specification.

   There are more types of anonymous boxes that arise when formatting
   tables.

  9.2.3 Run-in boxes

   [This section exists so that the section numbers are the same as in
   previous drafts. 'Display: run-in' is now defined in CSS level 3 (see
   CSS basic box model).]

  9.2.4 The 'display' property

   'display'

   Value:   inline | block | list-item | inline-block | table |
   inline-table | table-row-group | table-header-group |
   table-footer-group | table-row | table-column-group | table-column |
   table-cell | table-caption | none | inherit
   Initial:   inline
   Applies to:   all elements
   Inherited:   no
   Percentages:   N/A
   Media:   all
   Computed value:   see text

   The values of this property have the following meanings:

   block
          This value causes an element to generate a block box.

   inline-block
          This value causes an element to generate an inline-level block
          container. The inside of an inline-block is formatted as a block
          box, and the element itself is formatted as an atomic
          inline-level box.

   inline
          This value causes an element to generate one or more inline
          boxes.

   list-item
          This value causes an element (e.g., LI in HTML) to generate a
          principal block box and a marker box. For information about
          lists and examples of list formatting, please consult the
          section on lists.

   none
          This value causes an element to not appear in the formatting
          structure (i.e., in visual media the element generates no boxes
          and has no effect on layout). Descendant elements do not
          generate any boxes either; the element and its content are
          removed from the formatting structure entirely. This behavior
          cannot be overridden by setting the 'display' property on the
          descendants.

          Please note that a display of 'none' does not create an
          invisible box; it creates no box at all. CSS includes mechanisms
          that enable an element to generate boxes in the formatting
          structure that affect formatting but are not visible themselves.
          Please consult the section on visibility for details.

   table, inline-table, table-row-group, table-column, table-column-group,
          table-header-group, table-footer-group, table-row, table-cell,
          and table-caption
          These values cause an element to behave like a table element
          (subject to restrictions described in the chapter on tables).

   The computed value is the same as the specified value, except for
   positioned and floating elements (see Relationships between 'display',
   'position', and 'float') and for the root element. For the root
   element, the computed value is changed as described in the section on
   the relationships between 'display', 'position', and 'float'.

   Note that although the initial value of 'display' is 'inline', rules in
   the user agent's default style sheet may override this value. See the
   sample style sheet for HTML 4 in the appendix.

   Example(s):

   Here are some examples of the 'display' property:
p   { display: block }
em  { display: inline }
li  { display: list-item }
img { display: none }      /* Do not display images */

9.3 Positioning schemes

   In CSS 2.1, a box may be laid out according to three positioning
   schemes:
    1. Normal flow. In CSS 2.1, normal flow includes block formatting of
       block-level boxes, inline formatting of inline-level boxes, and
       relative positioning of block-level and inline-level boxes.
    2. Floats. In the float model, a box is first laid out according to
       the normal flow, then taken out of the flow and shifted to the left
       or right as far as possible. Content may flow along the side of a
       float.
    3. Absolute positioning. In the absolute positioning model, a box is
       removed from the normal flow entirely (it has no impact on later
       siblings) and assigned a position with respect to a containing
       block.

   An element is called out of flow if it is floated, absolutely
   positioned, or is the root element. An element is called in-flow if it
   is not out-of-flow. The flow of an element A is the set consisting of A
   and all in-flow elements whose nearest out-of-flow ancestor is A.

   Note. CSS 2.1's positioning schemes help authors make their documents
   more accessible by allowing them to avoid mark-up tricks (e.g.,
   invisible images) used for layout effects.

  9.3.1 Choosing a positioning scheme: 'position' property

   The 'position' and 'float' properties determine which of the CSS 2.1
   positioning algorithms is used to calculate the position of a box.

   'position'

          Value:            static | relative | absolute | fixed | inherit
          Initial:          static
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   The values of this property have the following meanings:

   static
          The box is a normal box, laid out according to the normal flow.
          The 'top', 'right', 'bottom', and 'left' properties do not
          apply.

   relative
          The box's position is calculated according to the normal flow
          (this is called the position in normal flow). Then the box is
          offset relative to its normal position. When a box B is
          relatively positioned, the position of the following box is
          calculated as though B were not offset. The effect of
          'position:relative' on table-row-group, table-header-group,
          table-footer-group, table-row, table-column-group, table-column,
          table-cell, and table-caption elements is undefined.

   absolute
          The box's position (and possibly size) is specified with the
          'top', 'right', 'bottom', and 'left' properties. These
          properties specify offsets with respect to the box's containing
          block. Absolutely positioned boxes are taken out of the normal
          flow. This means they have no impact on the layout of later
          siblings. Also, though absolutely positioned boxes have margins,
          they do not collapse with any other margins.

   fixed
          The box's position is calculated according to the 'absolute'
          model, but in addition, the box is fixed with respect to some
          reference. As with the 'absolute' model, the box's margins do
          not collapse with any other margins. In the case of handheld,
          projection, screen, tty, and tv media types, the box is fixed
          with respect to the viewport and does not move when scrolled. In
          the case of the print media type, the box is rendered on every
          page, and is fixed with respect to the page box, even if the
          page is seen through a viewport (in the case of a print-preview,
          for example). For other media types, the presentation is
          undefined. Authors may wish to specify 'fixed' in a
          media-dependent way. For instance, an author may want a box to
          remain at the top of the viewport on the screen, but not at the
          top of each printed page. The two specifications may be
          separated by using an @media rule, as in:

          Example(s):


@media screen {
  h1#first { position: fixed }
}
@media print {
  h1#first { position: static }
}

          UAs must not paginate the content of fixed boxes. Note that UAs
          may print invisible content in other ways. See "Content outside
          the page box" in chapter 13.

   User agents may treat position as 'static' on the root element.

  9.3.2 Box offsets: 'top', 'right', 'bottom', 'left'

   An element is said to be positioned if its 'position' property has a
   value other than 'static'. Positioned elements generate positioned
   boxes, laid out according to four properties:

   'top'

   Value:   <length> | <percentage> | auto | inherit
   Initial:   auto
   Applies to:   positioned elements
   Inherited:   no
   Percentages:   refer to height of containing block
   Media:   visual
   Computed value:   if specified as a length, the corresponding absolute
   length; if specified as a percentage, the specified value; otherwise,
   'auto'.

   This property specifies how far an absolutely positioned box's top
   margin edge is offset below the top edge of the box's containing block.
   For relatively positioned boxes, the offset is with respect to the top
   edges of the box itself (i.e., the box is given a position in the
   normal flow, then offset from that position according to these
   properties).

   'right'

   Value:   <length> | <percentage> | auto | inherit
   Initial:   auto
   Applies to:   positioned elements
   Inherited:   no
   Percentages:   refer to width of containing block
   Media:   visual
   Computed value:   if specified as a length, the corresponding absolute
   length; if specified as a percentage, the specified value; otherwise,
   'auto'.

   Like 'top', but specifies how far a box's right margin edge is offset
   to the left of the right edge of the box's containing block. For
   relatively positioned boxes, the offset is with respect to the right
   edge of the box itself.

   'bottom'

   Value:   <length> | <percentage> | auto | inherit
   Initial:   auto
   Applies to:   positioned elements
   Inherited:   no
   Percentages:   refer to height of containing block
   Media:   visual
   Computed value:   if specified as a length, the corresponding absolute
   length; if specified as a percentage, the specified value; otherwise,
   'auto'.

   Like 'top', but specifies how far a box's bottom margin edge is offset
   above the bottom of the box's containing block. For relatively
   positioned boxes, the offset is with respect to the bottom edge of the
   box itself.

   'left'

   Value:   <length> | <percentage> | auto | inherit
   Initial:   auto
   Applies to:   positioned elements
   Inherited:   no
   Percentages:   refer to width of containing block
   Media:   visual
   Computed value:   if specified as a length, the corresponding absolute
   length; if specified as a percentage, the specified value; otherwise,
   'auto'.

   Like 'top', but specifies how far a box's left margin edge is offset to
   the right of the left edge of the box's containing block. For
   relatively positioned boxes, the offset is with respect to the left
   edge of the box itself.

   The values for the four properties have the following meanings:

   <length>
          The offset is a fixed distance from the reference edge. Negative
          values are allowed.

   <percentage>
          The offset is a percentage of the containing block's width (for
          'left' or 'right') or height (for 'top' and 'bottom'). Negative
          values are allowed.

   auto
          For non-replaced elements, the effect of this value depends on
          which of related properties have the value 'auto' as well. See
          the sections on the width and height of absolutely positioned,
          non-replaced elements for details. For replaced elements, the
          effect of this value depends only on the intrinsic dimensions of
          the replaced content. See the sections on the width and height
          of absolutely positioned, replaced elements for details.

9.4 Normal flow

   Boxes in the normal flow belong to a formatting context, which may be
   block or inline, but not both simultaneously. Block-level boxes
   participate in a block formatting context. Inline-level boxes
   participate in an inline formatting context.

  9.4.1 Block formatting contexts

   Floats, absolutely positioned elements, block containers (such as
   inline-blocks, table-cells, and table-captions) that are not block
   boxes, and block boxes with 'overflow' other than 'visible' (except
   when that value has been propagated to the viewport) establish new
   block formatting contexts for their contents.

   In a block formatting context, boxes are laid out one after the other,
   vertically, beginning at the top of a containing block. The vertical
   distance between two sibling boxes is determined by the 'margin'
   properties. Vertical margins between adjacent block-level boxes in a
   block formatting context collapse.

   In a block formatting context, each box's left outer edge touches the
   left edge of the containing block (for right-to-left formatting, right
   edges touch). This is true even in the presence of floats (although a
   box's line boxes may shrink due to the floats), unless the box
   establishes a new block formatting context (in which case the box
   itself may become narrower due to the floats).

   For information about page breaks in paged media, please consult the
   section on allowed page breaks.

  9.4.2 Inline formatting contexts

   In an inline formatting context, boxes are laid out horizontally, one
   after the other, beginning at the top of a containing block. Horizontal
   margins, borders, and padding are respected between these boxes. The
   boxes may be aligned vertically in different ways: their bottoms or
   tops may be aligned, or the baselines of text within them may be
   aligned. The rectangular area that contains the boxes that form a line
   is called a line box.

   The width of a line box is determined by a containing block and the
   presence of floats. The height of a line box is determined by the rules
   given in the section on line height calculations.

   A line box is always tall enough for all of the boxes it contains.
   However, it may be taller than the tallest box it contains (if, for
   example, boxes are aligned so that baselines line up). When the height
   of a box B is less than the height of the line box containing it, the
   vertical alignment of B within the line box is determined by the
   'vertical-align' property. When several inline-level boxes cannot fit
   horizontally within a single line box, they are distributed among two
   or more vertically-stacked line boxes. Thus, a paragraph is a vertical
   stack of line boxes. Line boxes are stacked with no vertical separation
   (except as specified elsewhere) and they never overlap.

   In general, the left edge of a line box touches the left edge of its
   containing block and the right edge touches the right edge of its
   containing block. However, floating boxes may come between the
   containing block edge and the line box edge. Thus, although line boxes
   in the same inline formatting context generally have the same width
   (that of the containing block), they may vary in width if available
   horizontal space is reduced due to floats. Line boxes in the same
   inline formatting context generally vary in height (e.g., one line
   might contain a tall image while the others contain only text).

   When the total width of the inline-level boxes on a line is less than
   the width of the line box containing them, their horizontal
   distribution within the line box is determined by the 'text-align'
   property. If that property has the value 'justify', the user agent may
   stretch spaces and words in inline boxes (but not inline-table and
   inline-block boxes) as well.

   When an inline box exceeds the width of a line box, it is split into
   several boxes and these boxes are distributed across several line
   boxes. If an inline box cannot be split (e.g., if the inline box
   contains a single character, or language specific word breaking rules
   disallow a break within the inline box, or if the inline box is
   affected by a white-space value of nowrap or pre), then the inline box
   overflows the line box.

   When an inline box is split, margins, borders, and padding have no
   visual effect where the split occurs (or at any split, when there are
   several).

   Inline boxes may also be split into several boxes within the same line
   box due to bidirectional text processing.

   Line boxes are created as needed to hold inline-level content within an
   inline formatting context. Line boxes that contain no text, no
   preserved white space, no inline elements with non-zero margins,
   padding, or borders, and no other in-flow content (such as images,
   inline blocks or inline tables), and do not end with a preserved
   newline must be treated as zero-height line boxes for the purposes of
   determining the positions of any elements inside of them, and must be
   treated as not existing for any other purpose.

   Here is an example of inline box construction. The following paragraph
   (created by the HTML block-level element P) contains anonymous text
   interspersed with the elements EM and STRONG:
<P>Several <EM>emphasized words</EM> appear
<STRONG>in this</STRONG> sentence, dear.</P>

   The P element generates a block box that contains five inline boxes,
   three of which are anonymous:
     * Anonymous: "Several"
     * EM: "emphasized words"
     * Anonymous: "appear"
     * STRONG: "in this"
     * Anonymous: "sentence, dear."

   To format the paragraph, the user agent flows the five boxes into line
   boxes. In this example, the box generated for the P element establishes
   the containing block for the line boxes. If the containing block is
   sufficiently wide, all the inline boxes will fit into a single line
   box:
 Several emphasized words appear in this sentence, dear.

   If not, the inline boxes will be split up and distributed across
   several line boxes. The previous paragraph might be split as follows:
Several emphasized words appear
in this sentence, dear.

   or like this:
Several emphasized
words appear in this
sentence, dear.

   In the previous example, the EM box was split into two EM boxes (call
   them "split1" and "split2"). Margins, borders, padding, or text
   decorations have no visible effect after split1 or before split2.

   Consider the following example:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
    <TITLE>Example of inline flow on several lines</TITLE>
    <STYLE type="text/css">
      EM {
        padding: 2px;
        margin: 1em;
        border-width: medium;
        border-style: dashed;
        line-height: 2.4em;
      }
    </STYLE>
  </HEAD>
  <BODY>
    <P>Several <EM>emphasized words</EM> appear here.</P>
  </BODY>
</HTML>

   Depending on the width of the P, the boxes may be distributed as
   follows:

   Image illustrating the effect of line breaking on the display of
   margins, borders, and padding.    [D]
     * The margin is inserted before "emphasized" and after "words".
     * The padding is inserted before, above, and below "emphasized" and
       after, above, and below "words". A dashed border is rendered on
       three sides in each case.

  9.4.3 Relative positioning

   Once a box has been laid out according to the normal flow or floated,
   it may be shifted relative to this position. This is called relative
   positioning. Offsetting a box (B1) in this way has no effect on the box
   (B2) that follows: B2 is given a position as if B1 were not offset and
   B2 is not re-positioned after B1's offset is applied. This implies that
   relative positioning may cause boxes to overlap. However, if relative
   positioning causes an 'overflow:auto' or 'overflow:scroll' box to have
   overflow, the UA must allow the user to access this content (at its
   offset position), which, through the creation of scrollbars, may affect
   layout.

   A relatively positioned box keeps its normal flow size, including line
   breaks and the space originally reserved for it. The section on
   containing blocks explains when a relatively positioned box establishes
   a new containing block.

   For relatively positioned elements, 'left' and 'right' move the box(es)
   horizontally, without changing their size. 'Left' moves the boxes to
   the right, and 'right' moves them to the left. Since boxes are not
   split or stretched as a result of 'left' or 'right', the used values
   are always: left = -right.

   If both 'left' and 'right' are 'auto' (their initial values), the used
   values are '0' (i.e., the boxes stay in their original position).

   If 'left' is 'auto', its used value is minus the value of 'right'
   (i.e., the boxes move to the left by the value of 'right').

   If 'right' is specified as 'auto', its used value is minus the value of
   'left'.

   If neither 'left' nor 'right' is 'auto', the position is
   over-constrained, and one of them has to be ignored. If the 'direction'
   property of the containing block is 'ltr', the value of 'left' wins and
   'right' becomes -'left'. If 'direction' of the containing block is
   'rtl', 'right' wins and 'left' is ignored.

   Example(s):

   Example. The following three rules are equivalent:
div.a8 { position: relative; direction: ltr; left: -1em; right: auto }
div.a8 { position: relative; direction: ltr; left: auto; right: 1em }
div.a8 { position: relative; direction: ltr; left: -1em; right: 5em }

   The 'top' and 'bottom' properties move relatively positioned element(s)
   up or down without changing their size. 'Top' moves the boxes down, and
   'bottom' moves them up. Since boxes are not split or stretched as a
   result of 'top' or 'bottom', the used values are always: top = -bottom.
   If both are 'auto', their used values are both '0'. If one of them is
   'auto', it becomes the negative of the other. If neither is 'auto',
   'bottom' is ignored (i.e., the used value of 'bottom' will be minus the
   value of 'top').

   Note. Dynamic movement of relatively positioned boxes can produce
   animation effects in scripting environments (see also the 'visibility'
   property). Although relative positioning may be used as a form of
   superscripting and subscripting, the line height is not automatically
   adjusted to take the positioning into consideration. See the
   description of line height calculations for more information.

   Examples of relative positioning are provided in the section comparing
   normal flow, floats, and absolute positioning.

9.5 Floats

   A float is a box that is shifted to the left or right on the current
   line. The most interesting characteristic of a float (or "floated" or
   "floating" box) is that content may flow along its side (or be
   prohibited from doing so by the 'clear' property). Content flows down
   the right side of a left-floated box and down the left side of a
   right-floated box. The following is an introduction to float
   positioning and content flow; the exact rules governing float behavior
   are given in the description of the 'float' property.

   A floated box is shifted to the left or right until its outer edge
   touches the containing block edge or the outer edge of another float.
   If there is a line box, the outer top of the floated box is aligned
   with the top of the current line box.

   If there is not enough horizontal room for the float, it is shifted
   downward until either it fits or there are no more floats present.

   Since a float is not in the flow, non-positioned block boxes created
   before and after the float box flow vertically as if the float did not
   exist. However, the current and subsequent line boxes created next to
   the float are shortened as necessary to make room for the margin box of
   the float.

   A line box is next to a float when there exists a vertical position
   that satisfies all of these four conditions: (a) at or below the top of
   the line box, (b) at or above the bottom of the line box, (c) below the
   top margin edge of the float, and (d) above the bottom margin edge of
   the float.

   Note: this means that floats with zero outer height or negative outer
   height do not shorten line boxes.

   If a shortened line box is too small to contain any content, then the
   line box is shifted downward (and its width recomputed) until either
   some content fits or there are no more floats present. Any content in
   the current line before a floated box is reflowed in the same line on
   the other side of the float. In other words, if inline-level boxes are
   placed on the line before a left float is encountered that fits in the
   remaining line box space, the left float is placed on that line,
   aligned with the top of the line box, and then the inline-level boxes
   already on the line are moved accordingly to the right of the float
   (the right being the other side of the left float) and vice versa for
   rtl and right floats.

   The border box of a table, a block-level replaced element, or an
   element in the normal flow that establishes a new block formatting
   context (such as an element with 'overflow' other than 'visible') must
   not overlap the margin box of any floats in the same block formatting
   context as the element itself. If necessary, implementations should
   clear the said element by placing it below any preceding floats, but
   may place it adjacent to such floats if there is sufficient space. They
   may even make the border box of said element narrower than defined by
   section 10.3.3. CSS2 does not define when a UA may put said element
   next to the float or by how much said element may become narrower.

   Example(s):

   Example. In the following document fragment, the containing block is
   too narrow to contain the content next to the float, so the content
   gets moved to below the floats where it is aligned in the line box
   according to the text-align property.
p { width: 10em; border: solid aqua; }
span { float: left; width: 5em; height: 5em; border: solid blue; }


...


<p>
  <span> </span>
  Supercalifragilisticexpialidocious
</p>

   This fragment might look like this:

   Image illustrating the effect of an unbreakable piece of content being
   reflowed to just after a float which left insufficient room next to it
   for the content to fit.

   Several floats may be adjacent, and this model also applies to adjacent
   floats in the same line.

   Example(s):

   The following rule floats all IMG boxes with class="icon" to the left
   (and sets the left margin to '0'):
img.icon {
  float: left;
  margin-left: 0;
}

   Consider the following HTML source and style sheet:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
    <TITLE>Float example</TITLE>
    <STYLE type="text/css">
      IMG { float: left }
      BODY, P, IMG { margin: 2em }
    </STYLE>
  </HEAD>
  <BODY>
    <P><IMG src=img.png alt="This image will illustrate floats">
       Some sample text that has no other...
  </BODY>
</HTML>

   The IMG box is floated to the left. The content that follows is
   formatted to the right of the float, starting on the same line as the
   float. The line boxes to the right of the float are shortened due to
   the float's presence, but resume their "normal" width (that of the
   containing block established by the P element) after the float. This
   document might be formatted as:

   Image illustrating how floating boxes interact with margins.    [D]

   Formatting would have been exactly the same if the document had been:
<BODY>
  <P>Some sample text
  <IMG src=img.png alt="This image will illustrate floats">
           that has no other...
</BODY>

   because the content to the left of the float is displaced by the float
   and reflowed down its right side.

   As stated in section 8.3.1, the margins of floating boxes never
   collapse with margins of adjacent boxes. Thus, in the previous example,
   vertical margins do not collapse between the P box and the floated IMG
   box.

   The contents of floats are stacked as if floats generated new stacking
   contexts, except that any positioned elements and elements that
   actually create new stacking contexts take part in the float's parent
   stacking context. A float can overlap other boxes in the normal flow
   (e.g., when a normal flow box next to a float has negative margins).
   When this happens, floats are rendered in front of non-positioned
   in-flow blocks, but behind in-flow inlines.

   Example(s):

   Here is another illustration, showing what happens when a float
   overlaps borders of elements in the normal flow.

   Image showing a floating image that overlaps the borders of two
   paragraphs: the borders are interrupted by the image.    [D]

   A floating image obscures borders of block boxes it overlaps.

   The following example illustrates the use of the 'clear' property to
   prevent content from flowing next to a float.

   Example(s):

   Assuming a rule such as this:
p { clear: left }

   formatting might look like this:

   Image showing a floating image and the effect of 'clear: left' on the
   two paragraphs.    [D]

   Both paragraphs have set 'clear: left', which causes the second
   paragraph to be "pushed down" to a position below the float —
   "clearance" is added above its top margin to accomplish this (see the
   'clear' property).

  9.5.1 Positioning the float: the 'float' property

   'float'

          Value:            left | right | none | inherit
          Initial:          none
          Applies to:       all, but see 9.7
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property specifies whether a box should float to the left, right,
   or not at all. It may be set for any element, but only applies to
   elements that generate boxes that are not absolutely positioned. The
   values of this property have the following meanings:

   left
          The element generates a block box that is floated to the left.
          Content flows on the right side of the box, starting at the top
          (subject to the 'clear' property).

   right
          Similar to 'left', except the box is floated to the right, and
          content flows on the left side of the box, starting at the top.

   none
          The box is not floated.

   User agents may treat float as 'none' on the root element.

   Here are the precise rules that govern the behavior of floats:
    1. The left outer edge of a left-floating box may not be to the left
       of the left edge of its containing block. An analogous rule holds
       for right-floating elements.
    2. If the current box is left-floating, and there are any
       left-floating boxes generated by elements earlier in the source
       document, then for each such earlier box, either the left outer
       edge of the current box must be to the right of the right outer
       edge of the earlier box, or its top must be lower than the bottom
       of the earlier box. Analogous rules hold for right-floating boxes.
    3. The right outer edge of a left-floating box may not be to the right
       of the left outer edge of any right-floating box that is next to
       it. Analogous rules hold for right-floating elements.
    4. A floating box's outer top may not be higher than the top of its
       containing block. When the float occurs between two collapsing
       margins, the float is positioned as if it had an otherwise empty
       anonymous block parent taking part in the flow. The position of
       such a parent is defined by the rules in the section on margin
       collapsing.
    5. The outer top of a floating box may not be higher than the outer
       top of any block or floated box generated by an element earlier in
       the source document.
    6. The outer top of an element's floating box may not be higher than
       the top of any line-box containing a box generated by an element
       earlier in the source document.
    7. A left-floating box that has another left-floating box to its left
       may not have its right outer edge to the right of its containing
       block's right edge. (Loosely: a left float may not stick out at the
       right edge, unless it is already as far to the left as possible.)
       An analogous rule holds for right-floating elements.
    8. A floating box must be placed as high as possible.
    9. A left-floating box must be put as far to the left as possible, a
       right-floating box as far to the right as possible. A higher
       position is preferred over one that is further to the left/right.

   But in CSS 2.1, if, within the block formatting context, there is an
   in-flow negative vertical margin such that the float's position is
   above the position it would be at were all such negative margins set to
   zero, the position of the float is undefined.

   References to other elements in these rules refer only to other
   elements in the same block formatting context as the float.

   Example(s):

   This HTML fragment results in the b floating to the right.
<P>a<SPAN style="float: right">b</SPAN></P>

   If the P element's width is enough, the a and the b will be side by
   side. It might look like this:

   An a at the left side of a box and a b at the right side

  9.5.2 Controlling flow next to floats: the 'clear' property

   'clear'

          Value:            none | left | right | both | inherit
          Initial:          none
          Applies to:       block-level elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property indicates which sides of an element's box(es) may not be
   adjacent to an earlier floating box. The 'clear' property does not
   consider floats inside the element itself or in other block formatting
   contexts.

   Values have the following meanings when applied to non-floating
   block-level boxes:

   left
          Requires that the top border edge of the box be below the bottom
          outer edge of any left-floating boxes that resulted from
          elements earlier in the source document.

   right
          Requires that the top border edge of the box be below the bottom
          outer edge of any right-floating boxes that resulted from
          elements earlier in the source document.

   both
          Requires that the top border edge of the box be below the bottom
          outer edge of any right-floating and left-floating boxes that
          resulted from elements earlier in the source document.

   none
          No constraint on the box's position with respect to floats.

   Values other than 'none' potentially introduce clearance. Clearance
   inhibits margin collapsing and acts as spacing above the margin-top of
   an element. It is used to push the element vertically past the float.

   Computing the clearance of an element on which 'clear' is set is done
   by first determining the hypothetical position of the element's top
   border edge. This position is where the actual top border edge would
   have been if the element's 'clear' property had been 'none'.

   If this hypothetical position of the element's top border edge is not
   past the relevant floats, then clearance is introduced, and margins
   collapse according to the rules in 8.3.1.

   Then the amount of clearance is set to the greater of:
    1. The amount necessary to place the border edge of the block even
       with the bottom outer edge of the lowest float that is to be
       cleared.
    2. The amount necessary to place the top border edge of the block at
       its hypothetical position.

   Alternatively, clearance is set exactly to the amount necessary to
   place the border edge of the block even with the bottom outer edge of
   the lowest float that is to be cleared.

   Note: Both behaviors are allowed pending evaluation of their
   compatibility with existing Web content. A future CSS specification
   will require either one or the other.

   Note: The clearance can be negative or zero.

   Example(s):

   Example 1. Assume (for the sake of simplicity), that we have just three
   boxes, in this order: block B1 with a bottom margin of M1 (B1 has no
   children and no padding or border), floating block F with a height H,
   and block B2 with a top margin of M2 (no padding or border, no
   children). B2 has 'clear' set to 'both'. We also assume B2 is not
   empty.

   Without considering the 'clear' property on B2, we have the situation
   in the diagram below. The margins of B1 and B2 collapse. Let's say the
   bottom border edge of B1 is at y = 0, then the top of F is at y = M1,
   the top border edge of B2 is at y = max(M1,M2), and the bottom of F is
   at y = M1 + H.

   Float F extends into the margin above M2.

   We also assume that B2 is not below F, i.e., we are in the situation
   described in the spec where we need to add clearance. That means:

     max(M1,M2) < M1 + H

   We need to compute clearance C twice, C1 and C2, and keep the greater
   of the two: C = max(C1,C2). The first way is to put the top of B2 flush
   with the bottom of F, i.e., at y = M1 + H. That means, because the
   margins no longer collapse with a clearance between them:

     bottom of F = top border edge of B2 ⇔

     M1 + H = M1 + C1 + M2 ⇔

     C1 = M1 + H - M1 - M2

     = H - M2

   The second computation is to keep the top of B2 where it is, i.e., at y
   = max(M1,M2). That means:

     max(M1,M2) = M1 + C2 + M2 ⇔

     C2 = max(M1,M2) - M1 - M2

   We assumed that max(M1,M2) < M1 + H, which implies

     C2 = max(M1,M2) - M1 - M2 < M1 + H - M1 - M2 = H - M2 ⇒

     C2 < H - M2

   And, as C1 = H - M2, it follows that

     C2 < C1

   and hence

     C = max(C1,C2) = C1

   Example(s):

   Example 2. An example of negative clearance is this situation, in which
   the clearance is -1em. (Assume none of the elements have borders or
   padding):
<p style="margin-bottom: 4em">
  First paragraph.

<p style="float: left; height: 2em; margin: 0">
  Floating paragraph.

<p style="clear: left; margin-top: 3em">
  Last paragraph.

   Explanation: Without the 'clear', the first and last paragraphs'
   margins would collapse and the last paragraph's top border edge would
   be flush with the top of the floating paragraph. But the 'clear'
   requires the top border edge to be below the float, i.e., 2em lower.
   This means that clearance must be introduced. Accordingly, the margins
   no longer collapse and the amount of clearance is set so that clearance
   + margin-top = 2em, i.e., clearance = 2em - margin-top = 2em - 3em =
   -1em.

   When the property is set on floating elements, it results in a
   modification of the rules for positioning the float. An extra
   constraint (#10) is added:
     * The top outer edge of the float must be below the bottom outer edge
       of all earlier left-floating boxes (in the case of 'clear: left'),
       or all earlier right-floating boxes (in the case of 'clear:
       right'), or both ('clear: both').

   Note. This property applied to all elements in CSS1. Implementations
   may therefore have supported this property on all elements. In CSS2 and
   CSS 2.1 the 'clear' property only applies to block-level elements.
   Therefore authors should only use this property on block-level
   elements. If an implementation does support clear on inline elements,
   rather than setting a clearance as explained above, the implementation
   should force a break and effectively insert one or more empty line
   boxes (or shifting the new line box downward as described in section
   9.5) to move the top of the cleared inline's line box to below the
   respective floating box(es).

9.6 Absolute positioning

   In the absolute positioning model, a box is explicitly offset with
   respect to its containing block. It is removed from the normal flow
   entirely (it has no impact on later siblings). An absolutely positioned
   box establishes a new containing block for normal flow children and
   absolutely (but not fixed) positioned descendants. However, the
   contents of an absolutely positioned element do not flow around any
   other boxes. They may obscure the contents of another box (or be
   obscured themselves), depending on the stack levels of the overlapping
   boxes.

   References in this specification to an absolutely positioned element
   (or its box) imply that the element's 'position' property has the value
   'absolute' or 'fixed'.

  9.6.1 Fixed positioning

   Fixed positioning is a subcategory of absolute positioning. The only
   difference is that for a fixed positioned box, the containing block is
   established by the viewport. For continuous media, fixed boxes do not
   move when the document is scrolled. In this respect, they are similar
   to fixed background images. For paged media, boxes with fixed positions
   are repeated on every page. This is useful for placing, for instance, a
   signature at the bottom of each page. Boxes with fixed position that
   are larger than the page area are clipped. Parts of the fixed position
   box that are not visible in the initial containing block will not
   print.

   Authors may use fixed positioning to create frame-like presentations.
   Consider the following frame layout:

   Image illustrating a frame-like layout with position='fixed'.    [D]

   This might be achieved with the following HTML document and style
   rules:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
    <TITLE>A frame document with CSS 2.1</TITLE>
    <STYLE type="text/css" media="screen">
      BODY { height: 8.5in } /* Required for percentage heights below */
      #header {
        position: fixed;
        width: 100%;
        height: 15%;
        top: 0;
        right: 0;
        bottom: auto;
        left: 0;
      }
      #sidebar {
        position: fixed;
        width: 10em;
        height: auto;
        top: 15%;
        right: auto;
        bottom: 100px;
        left: 0;
      }
      #main {
        position: fixed;
        width: auto;
        height: auto;
        top: 15%;
        right: 0;
        bottom: 100px;
        left: 10em;
      }
      #footer {
        position: fixed;
        width: 100%;
        height: 100px;
        top: auto;
        right: 0;
        bottom: 0;
        left: 0;
      }
    </STYLE>
  </HEAD>
  <BODY>
    <DIV id="header"> ...  </DIV>
    <DIV id="sidebar"> ...  </DIV>
    <DIV id="main"> ...  </DIV>
    <DIV id="footer"> ...  </DIV>
  </BODY>
</HTML>

9.7 Relationships between 'display', 'position', and 'float'

   The three properties that affect box generation and layout — 'display',
   'position', and 'float' — interact as follows:
    1. If 'display' has the value 'none', then 'position' and 'float' do
       not apply. In this case, the element generates no box.
    2. Otherwise, if 'position' has the value 'absolute' or 'fixed', the
       box is absolutely positioned, the computed value of 'float' is
       'none', and display is set according to the table below. The
       position of the box will be determined by the 'top', 'right',
       'bottom' and 'left' properties and the box's containing block.
    3. Otherwise, if 'float' has a value other than 'none', the box is
       floated and 'display' is set according to the table below.
    4. Otherwise, if the element is the root element, 'display' is set
       according to the table below, except that it is undefined in
       CSS 2.1 whether a specified value of 'list-item' becomes a computed
       value of 'block' or 'list-item'.
    5. Otherwise, the remaining 'display' property values apply as
       specified.

                        Specified value                         Computed value
 inline-table                                                  table
 inline, table-row-group, table-column, table-column-group,
 table-header-group, table-footer-group, table-row, table-cell,
 table-caption, inline-block                                   block
 others                                                        same as specified

9.8 Comparison of normal flow, floats, and absolute positioning

   To illustrate the differences between normal flow, relative
   positioning, floats, and absolute positioning, we provide a series of
   examples based on the following HTML:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
    <TITLE>Comparison of positioning schemes</TITLE>
  </HEAD>
  <BODY>
    <P>Beginning of body contents.
      <SPAN id="outer"> Start of outer contents.
      <SPAN id="inner"> Inner contents.</SPAN>
      End of outer contents.</SPAN>
      End of body contents.
    </P>
  </BODY>
</HTML>

   In this document, we assume the following rules:
body { display: block; font-size:12px; line-height: 200%;
       width: 400px; height: 400px }
p    { display: block }
span { display: inline }

   The final positions of boxes generated by the outer and inner elements
   vary in each example. In each illustration, the numbers to the left of
   the illustration indicate the normal flow position of the double-spaced
   (for clarity) lines.

   Note. The diagrams in this section are illustrative and not to scale.
   They are meant to highlight the differences between the various
   positioning schemes in CSS 2.1, and are not intended to be reference
   renderings of the examples given.

  9.8.1 Normal flow

   Consider the following CSS declarations for outer and inner that do not
   alter the normal flow of boxes:
#outer { color: red }
#inner { color: blue }

   The P element contains all inline content: anonymous inline text and
   two SPAN elements. Therefore, all of the content will be laid out in an
   inline formatting context, within a containing block established by the
   P element, producing something like:

   Image illustrating the normal flow of text between parent and sibling
   boxes.    [D]

  9.8.2 Relative positioning

   To see the effect of relative positioning, we specify:
#outer { position: relative; top: -12px; color: red }
#inner { position: relative; top: 12px; color: blue }

   Text flows normally up to the outer element. The outer text is then
   flowed into its normal flow position and dimensions at the end of line
   1. Then, the inline boxes containing the text (distributed over three
   lines) are shifted as a unit by '-12px' (upwards).

   The contents of inner, as a child of outer, would normally flow
   immediately after the words "of outer contents" (on line 1.5). However,
   the inner contents are themselves offset relative to the outer contents
   by '12px' (downwards), back to their original position on line 2.

   Note that the content following outer is not affected by the relative
   positioning of outer.

   Image illustrating the effects of relative positioning on a box's
   content.    [D]

   Note also that had the offset of outer been '-24px', the text of outer
   and the body text would have overlapped.

  9.8.3 Floating a box

   Now consider the effect of floating the inner element's text to the
   right by means of the following rules:
#outer { color: red }
#inner { float: right; width: 130px; color: blue }

   Text flows normally up to the inner box, which is pulled out of the
   flow and floated to the right margin (its 'width' has been assigned
   explicitly). Line boxes to the left of the float are shortened, and the
   document's remaining text flows into them.

   Image illustrating the effects of floating a box.    [D]

   To show the effect of the 'clear' property, we add a sibling element to
   the example:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
    <TITLE>Comparison of positioning schemes II</TITLE>
  </HEAD>
  <BODY>
    <P>Beginning of body contents.
      <SPAN id=outer> Start of outer contents.
      <SPAN id=inner> Inner contents.</SPAN>
      <SPAN id=sibling> Sibling contents.</SPAN>
      End of outer contents.</SPAN>
      End of body contents.
    </P>
  </BODY>
</HTML>

   The following rules:
#inner { float: right; width: 130px; color: blue }
#sibling { color: red }

   cause the inner box to float to the right as before and the document's
   remaining text to flow into the vacated space:

   Image illustrating the effects of floating a box without setting the
   clear property to control the flow of text around the box.    [D]

   However, if the 'clear' property on the sibling element is set to
   'right' (i.e., the generated sibling box will not accept a position
   next to floating boxes to its right), the sibling content begins to
   flow below the float:
#inner { float: right; width: 130px; color: blue }
#sibling { clear: right; color: red }

   Image illustrating the effects of floating an element with setting the
   clear property to control the flow of text around the element.    [D]

  9.8.4 Absolute positioning

   Finally, we consider the effect of absolute positioning. Consider the
   following CSS declarations for outer and inner:
#outer {
    position: absolute;
    top: 200px; left: 200px;
    width: 200px;
    color: red;
}
#inner { color: blue }

   which cause the top of the outer box to be positioned with respect to
   its containing block. The containing block for a positioned box is
   established by the nearest positioned ancestor (or, if none exists, the
   initial containing block, as in our example). The top side of the outer
   box is '200px' below the top of the containing block and the left side
   is '200px' from the left side. The child box of outer is flowed
   normally with respect to its parent.

   Image illustrating the effects of absolutely positioning a box.    [D]

   The following example shows an absolutely positioned box that is a
   child of a relatively positioned box. Although the parent outer box is
   not actually offset, setting its 'position' property to 'relative'
   means that its box may serve as the containing block for positioned
   descendants. Since the outer box is an inline box that is split across
   several lines, the first inline box's top and left edges (depicted by
   thick dashed lines in the illustration below) serve as references for
   'top' and 'left' offsets.
#outer {
  position: relative;
  color: red
}
#inner {
  position: absolute;
  top: 200px; left: -100px;
  height: 130px; width: 130px;
  color: blue;
}

   This results in something like the following:

   Image illustrating the effects of absolutely positioning a box with
   respect to a containing block.    [D]

   If we do not position the outer box:
#outer { color: red }
#inner {
  position: absolute;
  top: 200px; left: -100px;
  height: 130px; width: 130px;
  color: blue;
}

   the containing block for inner becomes the initial containing block (in
   our example). The following illustration shows where the inner box
   would end up in this case.

   Image illustrating the effects of absolutely positioning a box with
   respect to a containing block established by a normally positioned
   parent.    [D]

   Relative and absolute positioning may be used to implement change bars,
   as shown in the following example. The following fragment:
<P style="position: relative; margin-right: 10px; left: 10px;">
I used two red hyphens to serve as a change bar. They
will "float" to the left of the line containing THIS
<SPAN style="position: absolute; top: auto; left: -1em; color: red;">--</SPAN>
word.</P>

   might result in something like:

   Image illustrating the use of floats to create a changebar effect.
   [D]

   First, the paragraph (whose containing block sides are shown in the
   illustration) is flowed normally. Then it is offset '10px' from the
   left edge of the containing block (thus, a right margin of '10px' has
   been reserved in anticipation of the offset). The two hyphens acting as
   change bars are taken out of the flow and positioned at the current
   line (due to 'top: auto'), '-1em' from the left edge of its containing
   block (established by the P in its final position). The result is that
   the change bars seem to "float" to the left of the current line.

9.9 Layered presentation

  9.9.1 Specifying the stack level: the 'z-index' property

   'z-index'

          Value:            auto | <integer> | inherit
          Initial:          auto
          Applies to:       positioned elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   For a positioned box, the 'z-index' property specifies:
    1. The stack level of the box in the current stacking context.
    2. Whether the box establishes a stacking context.

   Values have the following meanings:

   <integer>
          This integer is the stack level of the generated box in the
          current stacking context. The box also establishes a new
          stacking context.

   auto
          The stack level of the generated box in the current stacking
          context is 0. The box does not establish a new stacking context
          unless it is the root element.

   In this section, the expression "in front of" means closer to the user
   as the user faces the screen.

   In CSS 2.1, each box has a position in three dimensions. In addition to
   their horizontal and vertical positions, boxes lie along a "z-axis" and
   are formatted one on top of the other. Z-axis positions are
   particularly relevant when boxes overlap visually. This section
   discusses how boxes may be positioned along the z-axis.

   The order in which the rendering tree is painted onto the canvas is
   described in terms of stacking contexts. Stacking contexts can contain
   further stacking contexts. A stacking context is atomic from the point
   of view of its parent stacking context; boxes in other stacking
   contexts may not come between any of its boxes.

   Each box belongs to one stacking context. Each positioned box in a
   given stacking context has an integer stack level, which is its
   position on the z-axis relative other stack levels within the same
   stacking context. Boxes with greater stack levels are always formatted
   in front of boxes with lower stack levels. Boxes may have negative
   stack levels. Boxes with the same stack level in a stacking context are
   stacked back-to-front according to document tree order.

   The root element forms the root stacking context. Other stacking
   contexts are generated by any positioned element (including relatively
   positioned elements) having a computed value of 'z-index' other than
   'auto'. Stacking contexts are not necessarily related to containing
   blocks. In future levels of CSS, other properties may introduce
   stacking contexts, for example 'opacity' [CSS3COLOR].

   Within each stacking context, the following layers are painted in
   back-to-front order:
    1. the background and borders of the element forming the stacking
       context.
    2. the child stacking contexts with negative stack levels (most
       negative first).
    3. the in-flow, non-inline-level, non-positioned descendants.
    4. the non-positioned floats.
    5. the in-flow, inline-level, non-positioned descendants, including
       inline tables and inline blocks.
    6. the child stacking contexts with stack level 0 and the positioned
       descendants with stack level 0.
    7. the child stacking contexts with positive stack levels (least
       positive first).

   Within each stacking context, positioned elements with stack level 0
   (in layer 6), non-positioned floats (layer 4), inline blocks (layer 5),
   and inline tables (layer 5), are painted as if those elements
   themselves generated new stacking contexts, except that their
   positioned descendants and any would-be child stacking contexts take
   part in the current stacking context.

   This painting order is applied recursively to each stacking context.
   This description of stacking context painting order constitutes an
   overview of the detailed normative definition in Appendix E.

   In the following example, the stack levels of the boxes (named with
   their "id" attributes) are: "text2"=0, "image"=1, "text3"=2, and
   "text1"=3. The "text2" stack level is inherited from the root box. The
   others are specified with the 'z-index' property.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
    <TITLE>Z-order positioning</TITLE>
    <STYLE type="text/css">
      .pile {
        position: absolute;
        left: 2in;
        top: 2in;
        width: 3in;
        height: 3in;
      }
    </STYLE>
  </HEAD>
  <BODY>
    <P>
      <IMG id="image" class="pile"
           src="butterfly.png" alt="A butterfly image"
           style="z-index: 1">

    <DIV id="text1" class="pile"
         style="z-index: 3">
      This text will overlay the butterfly image.
    </DIV>

    <DIV id="text2">
      This text will be beneath everything.
    </DIV>

    <DIV id="text3" class="pile"
         style="z-index: 2">
      This text will underlay text1, but overlay the butterfly image
    </DIV>
  </BODY>
</HTML>

   This example demonstrates the notion of transparency. The default
   behavior of the background is to allow boxes behind it to be visible.
   In the example, each box transparently overlays the boxes below it.
   This behavior can be overridden by using one of the existing background
   properties.

9.10 Text direction: the 'direction' and 'unicode-bidi' properties

   Conforming user agents that do not support bidirectional text may
   ignore the 'direction' and 'unicode-bidi' properties described in this
   section. This exception includes UAs that render right-to-left
   characters simply because a font on the system contains them but do not
   support the concept of right-to-left text direction.

   The characters in certain scripts are written from right to left. In
   some documents, in particular those written with the Arabic or Hebrew
   script, and in some mixed-language contexts, text in a single (visually
   displayed) block may appear with mixed directionality. This phenomenon
   is called bidirectionality, or "bidi" for short.

   The Unicode standard ([UNICODE], [UAX9]) defines a complex algorithm
   for determining the proper directionality of text. The algorithm
   consists of an implicit part based on character properties, as well as
   explicit controls for embeddings and overrides. CSS 2.1 relies on this
   algorithm to achieve proper bidirectional rendering. The 'direction'
   and 'unicode-bidi' properties allow authors to specify how the elements
   and attributes of a document language map to this algorithm.

   User agents that support bidirectional text must apply the Unicode
   bidirectional algorithm to every sequence of inline-level boxes
   uninterrupted by a forced (bidi class B) break or block boundary. This
   sequence forms the "paragraph" unit in the bidirectional algorithm. The
   paragraph embedding level is set according to the value of the
   'direction' property of the containing block rather than by the
   heuristic given in steps P2 and P3 of the Unicode algorithm.

   Because the directionality of a text depends on the structure and
   semantics of the document language, these properties should in most
   cases be used only by designers of document type descriptions (DTDs),
   or authors of special documents. If a default style sheet specifies
   these properties, authors and users should not specify rules to
   override them.

   The HTML 4 specification ([HTML4], section 8.2) defines
   bidirectionality behavior for HTML elements. The style sheet rules that
   would achieve the bidi behavior specified in [HTML4] are given in the
   sample style sheet. The HTML 4 specification also contains more
   information on bidirectionality issues.

   'direction'

          Value:            ltr | rtl | inherit
          Initial:          ltr
          Applies to:       all elements, but see prose
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property specifies the base writing direction of blocks and the
   direction of embeddings and overrides (see 'unicode-bidi') for the
   Unicode bidirectional algorithm. In addition, it specifies such things
   as the direction of table column layout, the direction of horizontal
   overflow, the position of an incomplete last line in a block in case of
   'text-align: justify'.

   Values for this property have the following meanings:

   ltr
          Left-to-right direction.

   rtl
          Right-to-left direction.

   For the 'direction' property to affect reordering in inline elements,
   the 'unicode-bidi' property's value must be 'embed' or 'override'.

   Note. The 'direction' property, when specified for table column
   elements, is not inherited by cells in the column since columns are not
   the ancestors of the cells in the document tree. Thus, CSS cannot
   easily capture the "dir" attribute inheritance rules described in
   [HTML4], section 11.3.2.1.

   'unicode-bidi'

          Value:            normal | embed | bidi-override | inherit
          Initial:          normal
          Applies to:       all elements, but see prose
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   Values for this property have the following meanings:

   normal
          The element does not open an additional level of embedding with
          respect to the bidirectional algorithm. For inline elements,
          implicit reordering works across element boundaries.

   embed
          If the element is inline, this value opens an additional level
          of embedding with respect to the bidirectional algorithm. The
          direction of this embedding level is given by the 'direction'
          property. Inside the element, reordering is done implicitly.
          This corresponds to adding a LRE (U+202A; for 'direction: ltr')
          or RLE (U+202B; for 'direction: rtl') at the start of the
          element and a PDF (U+202C) at the end of the element.

   bidi-override
          For inline elements this creates an override. For block
          container elements this creates an override for inline-level
          descendants not within another block container element. This
          means that inside the element, reordering is strictly in
          sequence according to the 'direction' property; the implicit
          part of the bidirectional algorithm is ignored. This corresponds
          to adding a LRO (U+202D; for 'direction: ltr') or RLO (U+202E;
          for 'direction: rtl') at the start of the element or at the
          start of each anonymous child block box, if any, and a PDF
          (U+202C) at the end of the element.

   The final order of characters in each block container is the same as if
   the bidi control codes had been added as described above, markup had
   been stripped, and the resulting character sequence had been passed to
   an implementation of the Unicode bidirectional algorithm for plain text
   that produced the same line-breaks as the styled text. In this process,
   replaced elements with 'display: inline' are treated as neutral
   characters, unless their 'unicode-bidi' property has a value other than
   'normal', in which case they are treated as strong characters in the
   'direction' specified for the element. All other atomic inline-level
   boxes are treated as neutral characters always.

   Please note that in order to be able to flow inline boxes in a uniform
   direction (either entirely left-to-right or entirely right-to-left),
   more inline boxes (including anonymous inline boxes) may have to be
   created, and some inline boxes may have to be split up and reordered
   before flowing.

   Because the Unicode algorithm has a limit of 61 levels of embedding,
   care should be taken not to use 'unicode-bidi' with a value other than
   'normal' unless appropriate. In particular, a value of 'inherit' should
   be used with extreme caution. However, for elements that are, in
   general, intended to be displayed as blocks, a setting of
   'unicode-bidi: embed' is preferred to keep the element together in case
   display is changed to inline (see example below).

   The following example shows an XML document with bidirectional text. It
   illustrates an important design principle: DTD designers should take
   bidi into account both in the language proper (elements and attributes)
   and in any accompanying style sheets. The style sheets should be
   designed so that bidi rules are separate from other style rules. The
   bidi rules should not be overridden by other style sheets so that the
   document language's or DTD's bidi behavior is preserved.

   Example(s):

   In this example, lowercase letters stand for inherently left-to-right
   characters and uppercase letters represent inherently right-to-left
   characters:
<HEBREW>
  <PAR>HEBREW1 HEBREW2 english3 HEBREW4 HEBREW5</PAR>
  <PAR>HEBREW6 <EMPH>HEBREW7</EMPH> HEBREW8</PAR>
</HEBREW>
<ENGLISH>
  <PAR>english9 english10 english11 HEBREW12 HEBREW13</PAR>
  <PAR>english14 english15 english16</PAR>
  <PAR>english17 <HE-QUO>HEBREW18 english19 HEBREW20</HE-QUO></PAR>
</ENGLISH>

   Since this is XML, the style sheet is responsible for setting the
   writing direction. This is the style sheet:
/* Rules for bidi */
HEBREW, HE-QUO  {direction: rtl; unicode-bidi: embed}
ENGLISH         {direction: ltr; unicode-bidi: embed}

/* Rules for presentation */
HEBREW, ENGLISH, PAR  {display: block}
EMPH                  {font-weight: bold}

   The HEBREW element is a block with a right-to-left base direction, the
   ENGLISH element is a block with a left-to-right base direction. The
   PARs are blocks that inherit the base direction from their parents.
   Thus, the first two PARs are read starting at the top right, the final
   three are read starting at the top left. Please note that HEBREW and
   ENGLISH are chosen as element names for explicitness only; in general,
   element names should convey structure without reference to language.

   The EMPH element is inline-level, and since its value for
   'unicode-bidi' is 'normal' (the initial value), it has no effect on the
   ordering of the text. The HE-QUO element, on the other hand, creates an
   embedding.

   The formatting of this text might look like this if the line length is
   long:
               5WERBEH 4WERBEH english3 2WERBEH 1WERBEH

                                8WERBEH 7WERBEH 6WERBEH

english9 english10 english11 13WERBEH 12WERBEH

english14 english15 english16

english17 20WERBEH english19 18WERBEH

   Note that the HE-QUO embedding causes HEBREW18 to be to the right of
   english19.

   If lines have to be broken, it might be more like this:
       2WERBEH 1WERBEH
  -EH 4WERBEH english3
                 5WERB

   -EH 7WERBEH 6WERBEH
                 8WERB

english9 english10 en-
glish11 12WERBEH
13WERBEH

english14 english15
english16

english17 18WERBEH
20WERBEH english19

   Because HEBREW18 must be read before english19, it is on the line above
   english19. Just breaking the long line from the earlier formatting
   would not have worked. Note also that the first syllable from english19
   might have fit on the previous line, but hyphenation of left-to-right
   words in a right-to-left context, and vice versa, is usually suppressed
   to avoid having to display a hyphen in the middle of a line.

                       10 Visual formatting model details

   Contents
     * 10.1 Definition of "containing block"
     * 10.2 Content width: the 'width' property
     * 10.3 Calculating widths and margins
          + 10.3.1 Inline, non-replaced elements
          + 10.3.2 Inline, replaced elements
          + 10.3.3 Block-level, non-replaced elements in normal flow
          + 10.3.4 Block-level, replaced elements in normal flow
          + 10.3.5 Floating, non-replaced elements
          + 10.3.6 Floating, replaced elements
          + 10.3.7 Absolutely positioned, non-replaced elements
          + 10.3.8 Absolutely positioned, replaced elements
          + 10.3.9 'Inline-block', non-replaced elements in normal flow
          + 10.3.10 'Inline-block', replaced elements in normal flow
     * 10.4 Minimum and maximum widths: 'min-width' and 'max-width'
     * 10.5 Content height: the 'height' property
     * 10.6 Calculating heights and margins
          + 10.6.1 Inline, non-replaced elements
          + 10.6.2 Inline replaced elements, block-level replaced elements
            in normal flow, 'inline-block' replaced elements in normal
            flow and floating replaced elements
          + 10.6.3 Block-level non-replaced elements in normal flow when
            'overflow' computes to 'visible'
          + 10.6.4 Absolutely positioned, non-replaced elements
          + 10.6.5 Absolutely positioned, replaced elements
          + 10.6.6 Complicated cases
          + 10.6.7 'Auto' heights for block formatting context roots
     * 10.7 Minimum and maximum heights: 'min-height' and 'max-height'
     * 10.8 Line height calculations: the 'line-height' and
       'vertical-align' properties
          + 10.8.1 Leading and half-leading

10.1 Definition of "containing block"

   The position and size of an element's box(es) are sometimes calculated
   relative to a certain rectangle, called the containing block of the
   element. The containing block of an element is defined as follows:
    1. The containing block in which the root element lives is a rectangle
       called the initial containing block. For continuous media, it has
       the dimensions of the viewport and is anchored at the canvas
       origin; it is the page area for paged media. The 'direction'
       property of the initial containing block is the same as for the
       root element.
    2. For other elements, if the element's position is 'relative' or
       'static', the containing block is formed by the content edge of the
       nearest block container ancestor box.
    3. If the element has 'position: fixed', the containing block is
       established by the viewport in the case of continuous media or the
       page area in the case of paged media.
    4. If the element has 'position: absolute', the containing block is
       established by the nearest ancestor with a 'position' of
       'absolute', 'relative' or 'fixed', in the following way:
         1. In the case that the ancestor is an inline element, the
            containing block is the bounding box around the padding boxes
            of the first and the last inline boxes generated for that
            element. In CSS 2.1, if the inline element is split across
            multiple lines, the containing block is undefined.
         2. Otherwise, the containing block is formed by the padding edge
            of the ancestor.
       If there is no such ancestor, the containing block is the initial
       containing block.

   In paged media, an absolutely positioned element is positioned relative
   to its containing block ignoring any page breaks (as if the document
   were continuous). The element may subsequently be broken over several
   pages.

   For absolutely positioned content that resolves to a position on a page
   other than the page being laid out (the current page), or resolves to a
   position on the current page which has already been rendered for
   printing, printers may place the content
     * on another location on the current page,
     * on a subsequent page, or
     * may omit it.

   Note that a block-level element that is split over several pages may
   have a different width on each page and that there may be
   device-specific limits.

   Example(s):

   With no positioning, the containing blocks (C.B.) in the following
   document:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
   <HEAD>
      <TITLE>Illustration of containing blocks</TITLE>
   </HEAD>
   <BODY id="body">
      <DIV id="div1">
      <P id="p1">This is text in the first paragraph...</P>
      <P id="p2">This is text <EM id="em1"> in the
      <STRONG id="strong1">second</STRONG> paragraph.</EM></P>
      </DIV>
   </BODY>
</HTML>

   are established as follows:
   For box generated by C.B. is established by
   html                 initial C.B. (UA-dependent)
   body                 html
   div1                 body
   p1                   div1
   p2                   div1
   em1                  p2
   strong1              p2

   If we position "div1":
   #div1 { position: absolute; left: 50px; top: 50px }

   its containing block is no longer "body"; it becomes the initial
   containing block (since there are no other positioned ancestor boxes).

   If we position "em1" as well:
   #div1 { position: absolute; left: 50px; top: 50px }
   #em1  { position: absolute; left: 100px; top: 100px }

   the table of containing blocks becomes:
   For box generated by C.B. is established by
   html                 initial C.B. (UA-dependent)
   body                 html
   div1                 initial C.B.
   p1                   div1
   p2                   div1
   em1                  div1
   strong1              em1

   By positioning "em1", its containing block becomes the nearest
   positioned ancestor box (i.e., that generated by "div1").

10.2 Content width: the 'width' property

   'width'

         Value:            <length> | <percentage> | auto | inherit
         Initial:          auto
         Applies to:       all elements but non-replaced inline elements, table
                           rows, and row groups
         Inherited:        no
         Percentages:      refer to width of containing block
         Media:            visual
         Computed value:   the percentage or 'auto' as specified or the absolute
                           length

   This property specifies the content width of boxes.

   This property does not apply to non-replaced inline elements. The
   content width of a non-replaced inline element's boxes is that of the
   rendered content within them (before any relative offset of children).
   Recall that inline boxes flow into line boxes. The width of line boxes
   is given by the their containing block, but may be shorted by the
   presence of floats.

   Values have the following meanings:

   <length>
          Specifies the width of the content area using a length unit.

   <percentage>
          Specifies a percentage width. The percentage is calculated with
          respect to the width of the generated box's containing block. If
          the containing block's width depends on this element's width,
          then the resulting layout is undefined in CSS 2.1. Note: For
          absolutely positioned elements whose containing block is based
          on a block container element, the percentage is calculated with
          respect to the width of the padding box of that element. This is
          a change from CSS1, where the percentage width was always
          calculated with respect to the content box of the parent
          element.

   auto
          The width depends on the values of other properties. See the
          sections below.

   Negative values for 'width' are illegal.

   Example(s):

   For example, the following rule fixes the content width of paragraphs
   at 100 pixels:
p { width: 100px }

10.3 Calculating widths and margins

   The values of an element's 'width', 'margin-left', 'margin-right',
   'left' and 'right' properties as used for layout depend on the type of
   box generated and on each other. (The value used for layout is
   sometimes referred to as the used value.) In principle, the values used
   are the same as the computed values, with 'auto' replaced by some
   suitable value, and percentages calculated based on the containing
   block, but there are exceptions. The following situations need to be
   distinguished:
    1. inline, non-replaced elements
    2. inline, replaced elements
    3. block-level, non-replaced elements in normal flow
    4. block-level, replaced elements in normal flow
    5. floating, non-replaced elements
    6. floating, replaced elements
    7. absolutely positioned, non-replaced elements
    8. absolutely positioned, replaced elements
    9. 'inline-block', non-replaced elements in normal flow
   10. 'inline-block', replaced elements in normal flow

   For Points 1-6 and 9-10, the values of 'left' and 'right' in the case
   of relatively positioned elements are determined by the rules in
   section 9.4.3.

   Note. The used value of 'width' calculated below is a tentative value,
   and may have to be calculated multiple times, depending on 'min-width'
   and 'max-width', see the section Minimum and maximum widths below.

  10.3.1 Inline, non-replaced elements

   The 'width' property does not apply. A computed value of 'auto' for
   'margin-left' or 'margin-right' becomes a used value of '0'.

  10.3.2 Inline, replaced elements

   A computed value of 'auto' for 'margin-left' or 'margin-right' becomes
   a used value of '0'.

   If 'height' and 'width' both have computed values of 'auto' and the
   element also has an intrinsic width, then that intrinsic width is the
   used value of 'width'.

   If 'height' and 'width' both have computed values of 'auto' and the
   element has no intrinsic width, but does have an intrinsic height and
   intrinsic ratio; or if 'width' has a computed value of 'auto', 'height'
   has some other computed value, and the element does have an intrinsic
   ratio; then the used value of 'width' is:

     (used height) * (intrinsic ratio)

   If 'height' and 'width' both have computed values of 'auto' and the
   element has an intrinsic ratio but no intrinsic height or width, then
   the used value of 'width' is undefined in CSS 2.1. However, it is
   suggested that, if the containing block's width does not itself depend
   on the replaced element's width, then the used value of 'width' is
   calculated from the constraint equation used for block-level,
   non-replaced elements in normal flow.

   Otherwise, if 'width' has a computed value of 'auto', and the element
   has an intrinsic width, then that intrinsic width is the used value of
   'width'.

   Otherwise, if 'width' has a computed value of 'auto', but none of the
   conditions above are met, then the used value of 'width' becomes 300px.
   If 300px is too wide to fit the device, UAs should use the width of the
   largest rectangle that has a 2:1 ratio and fits the device instead.

  10.3.3 Block-level, non-replaced elements in normal flow

   The following constraints must hold among the used values of the other
   properties:

     'margin-left' + 'border-left-width' + 'padding-left' + 'width' +
     'padding-right' + 'border-right-width' + 'margin-right' = width of
     containing block

   If 'width' is not 'auto' and 'border-left-width' + 'padding-left' +
   'width' + 'padding-right' + 'border-right-width' (plus any of
   'margin-left' or 'margin-right' that are not 'auto') is larger than the
   width of the containing block, then any 'auto' values for 'margin-left'
   or 'margin-right' are, for the following rules, treated as zero.

   If all of the above have a computed value other than 'auto', the values
   are said to be "over-constrained" and one of the used values will have
   to be different from its computed value. If the 'direction' property of
   the containing block has the value 'ltr', the specified value of
   'margin-right' is ignored and the value is calculated so as to make the
   equality true. If the value of 'direction' is 'rtl', this happens to
   'margin-left' instead.

   If there is exactly one value specified as 'auto', its used value
   follows from the equality.

   If 'width' is set to 'auto', any other 'auto' values become '0' and
   'width' follows from the resulting equality.

   If both 'margin-left' and 'margin-right' are 'auto', their used values
   are equal. This horizontally centers the element with respect to the
   edges of the containing block.

  10.3.4 Block-level, replaced elements in normal flow

   The used value of 'width' is determined as for inline replaced
   elements. Then the rules for non-replaced block-level elements are
   applied to determine the margins.

  10.3.5 Floating, non-replaced elements

   If 'margin-left', or 'margin-right' are computed as 'auto', their used
   value is '0'.

   If 'width' is computed as 'auto', the used value is the "shrink-to-fit"
   width.

   Calculation of the shrink-to-fit width is similar to calculating the
   width of a table cell using the automatic table layout algorithm.
   Roughly: calculate the preferred width by formatting the content
   without breaking lines other than where explicit line breaks occur, and
   also calculate the preferred minimum width, e.g., by trying all
   possible line breaks. CSS 2.1 does not define the exact algorithm.
   Thirdly, find the available width: in this case, this is the width of
   the containing block minus the used values of 'margin-left',
   'border-left-width', 'padding-left', 'padding-right',
   'border-right-width', 'margin-right', and the widths of any relevant
   scroll bars.

   Then the shrink-to-fit width is: min(max(preferred minimum width,
   available width), preferred width).

  10.3.6 Floating, replaced elements

   If 'margin-left' or 'margin-right' are computed as 'auto', their used
   value is '0'. The used value of 'width' is determined as for inline
   replaced elements.

  10.3.7 Absolutely positioned, non-replaced elements

   For the purposes of this section and the next, the term "static
   position" (of an element) refers, roughly, to the position an element
   would have had in the normal flow. More precisely:
     * The static-position containing block is the containing block of a
       hypothetical box that would have been the first box of the element
       if its specified 'position' value had been 'static' and its
       specified 'float' had been 'none'. (Note that due to the rules in
       section 9.7 this hypothetical calculation might require also
       assuming a different computed value for 'display'.)
     * The static position for 'left' is the distance from the left edge
       of the containing block to the left margin edge of a hypothetical
       box that would have been the first box of the element if its
       'position' property had been 'static' and 'float' had been 'none'.
       The value is negative if the hypothetical box is to the left of the
       containing block.
     * The static position for 'right' is the distance from the right edge
       of the containing block to the right margin edge of the same
       hypothetical box as above. The value is positive if the
       hypothetical box is to the left of the containing block's edge.

   But rather than actually calculating the dimensions of that
   hypothetical box, user agents are free to make a guess at its probable
   position.

   For the purposes of calculating the static position, the containing
   block of fixed positioned elements is the initial containing block
   instead of the viewport, and all scrollable boxes should be assumed to
   be scrolled to their origin.

   The constraint that determines the used values for these elements is:

     'left' + 'margin-left' + 'border-left-width' + 'padding-left' +
     'width' + 'padding-right' + 'border-right-width' + 'margin-right' +
     'right' = width of containing block

   If all three of 'left', 'width', and 'right' are 'auto': First set any
   'auto' values for 'margin-left' and 'margin-right' to 0. Then, if the
   'direction' property of the element establishing the static-position
   containing block is 'ltr' set 'left' to the static position and apply
   rule number three below; otherwise, set 'right' to the static position
   and apply rule number one below.

   If none of the three is 'auto': If both 'margin-left' and
   'margin-right' are 'auto', solve the equation under the extra
   constraint that the two margins get equal values, unless this would
   make them negative, in which case when direction of the containing
   block is 'ltr' ('rtl'), set 'margin-left' ('margin-right') to zero and
   solve for 'margin-right' ('margin-left'). If one of 'margin-left' or
   'margin-right' is 'auto', solve the equation for that value. If the
   values are over-constrained, ignore the value for 'left' (in case the
   'direction' property of the containing block is 'rtl') or 'right' (in
   case 'direction' is 'ltr') and solve for that value.

   Otherwise, set 'auto' values for 'margin-left' and 'margin-right' to 0,
   and pick the one of the following six rules that applies.
    1. 'left' and 'width' are 'auto' and 'right' is not 'auto', then the
       width is shrink-to-fit. Then solve for 'left'
    2. 'left' and 'right' are 'auto' and 'width' is not 'auto', then if
       the 'direction' property of the element establishing the
       static-position containing block is 'ltr' set 'left' to the static
       position, otherwise set 'right' to the static position. Then solve
       for 'left' (if 'direction is 'rtl') or 'right' (if 'direction' is
       'ltr').
    3. 'width' and 'right' are 'auto' and 'left' is not 'auto', then the
       width is shrink-to-fit . Then solve for 'right'
    4. 'left' is 'auto', 'width' and 'right' are not 'auto', then solve
       for 'left'
    5. 'width' is 'auto', 'left' and 'right' are not 'auto', then solve
       for 'width'
    6. 'right' is 'auto', 'left' and 'width' are not 'auto', then solve
       for 'right'

   Calculation of the shrink-to-fit width is similar to calculating the
   width of a table cell using the automatic table layout algorithm.
   Roughly: calculate the preferred width by formatting the content
   without breaking lines other than where explicit line breaks occur, and
   also calculate the preferred minimum width, e.g., by trying all
   possible line breaks. CSS 2.1 does not define the exact algorithm.
   Thirdly, calculate the available width: this is found by solving for
   'width' after setting 'left' (in case 1) or 'right' (in case 3) to 0.

   Then the shrink-to-fit width is: min(max(preferred minimum width,
   available width), preferred width).

  10.3.8 Absolutely positioned, replaced elements

   In this case, section 10.3.7 applies up through and including the
   constraint equation, but the rest of section 10.3.7 is replaced by the
   following rules:
    1. The used value of 'width' is determined as for inline replaced
       elements. If 'margin-left' or 'margin-right' is specified as 'auto'
       its used value is determined by the rules below.
    2. If both 'left' and 'right' have the value 'auto', then if the
       'direction' property of the element establishing the
       static-position containing block is 'ltr', set 'left' to the static
       position; else if 'direction' is 'rtl', set 'right' to the static
       position.
    3. If 'left' or 'right' are 'auto', replace any 'auto' on
       'margin-left' or 'margin-right' with '0'.
    4. If at this point both 'margin-left' and 'margin-right' are still
       'auto', solve the equation under the extra constraint that the two
       margins must get equal values, unless this would make them
       negative, in which case when the direction of the containing block
       is 'ltr' ('rtl'), set 'margin-left' ('margin-right') to zero and
       solve for 'margin-right' ('margin-left').
    5. If at this point there is an 'auto' left, solve the equation for
       that value.
    6. If at this point the values are over-constrained, ignore the value
       for either 'left' (in case the 'direction' property of the
       containing block is 'rtl') or 'right' (in case 'direction' is
       'ltr') and solve for that value.

  10.3.9 'Inline-block', non-replaced elements in normal flow

   If 'width' is 'auto', the used value is the shrink-to-fit width as for
   floating elements.

   A computed value of 'auto' for 'margin-left' or 'margin-right' becomes
   a used value of '0'.

  10.3.10 'Inline-block', replaced elements in normal flow

   Exactly as inline replaced elements.

10.4 Minimum and maximum widths: 'min-width' and 'max-width'

   'min-width'

          Value:            <length> | <percentage> | inherit
          Initial:          0
          Applies to:       all elements but non-replaced inline elements, table
                            rows, and row groups
          Inherited:        no
          Percentages:      refer to width of containing block
          Media:            visual
          Computed value:   the percentage as specified or the absolute length

   'max-width'

         Value:            <length> | <percentage> | none | inherit
         Initial:          none
         Applies to:       all elements but non-replaced inline elements, table
                           rows, and row groups
         Inherited:        no
         Percentages:      refer to width of containing block
         Media:            visual
         Computed value:   the percentage as specified or the absolute length or
                           'none'

   These two properties allow authors to constrain content widths to a
   certain range. Values have the following meanings:

   <length>
          Specifies a fixed minimum or maximum used width.

   <percentage>
          Specifies a percentage for determining the used value. The
          percentage is calculated with respect to the width of the
          generated box's containing block. If the containing block's
          width is negative, the used value is zero. If the containing
          block's width depends on this element's width, then the
          resulting layout is undefined in CSS 2.1.

   none
          (Only on 'max-width') No limit on the width of the box.

   Negative values for 'min-width' and 'max-width' are illegal.

   In CSS 2.1, the effect of 'min-width' and 'max-width' on tables, inline
   tables, table cells, table columns, and column groups is undefined.

   The following algorithm describes how the two properties influence the
   used value of the 'width' property:
    1. The tentative used width is calculated (without 'min-width' and
       'max-width') following the rules under "Calculating widths and
       margins" above.
    2. If the tentative used width is greater than 'max-width', the rules
       above are applied again, but this time using the computed value of
       'max-width' as the computed value for 'width'.
    3. If the resulting width is smaller than 'min-width', the rules above
       are applied again, but this time using the value of 'min-width' as
       the computed value for 'width'.

   These steps do not affect the real computed values of the above
   properties.

   However, for replaced elements with an intrinsic ratio and both 'width'
   and 'height' specified as 'auto', the algorithm is as follows:

   Select from the table the resolved height and width values for the
   appropriate constraint violation. Take the max-width and max-height as
   max(min, max) so that min ≤ max holds true. In this table w and h stand
   for the results of the width and height computations ignoring the
   'min-width', 'min-height', 'max-width' and 'max-height' properties.
   Normally these are the intrinsic width and height, but they may not be
   in the case of replaced elements with intrinsic ratios.

   Note: In cases where an explicit width or height is set and the other
   dimension is auto, applying a minimum or maximum constraint on the auto
   side can cause an over-constrained situation. The spec is clear in the
   behavior but it might not be what the author expects. The CSS3
   object-fit property can be used to obtain different results in this
   situation.

   Constraint Violation Resolved Width Resolved Height
   none w h
   w > max-width max-width max(max-width * h/w, min-height)
   w < min-width min-width min(min-width * h/w, max-height)
   h > max-height max(max-height * w/h, min-width) max-height
   h < min-height min(min-height * w/h, max-width) min-height
   (w > max-width) and (h > max-height), where
   (max-width/w ≤ max-height/h) max-width max(min-height, max-width * h/w)
   (w > max-width) and (h > max-height), where
   (max-width/w > max-height/h) max(min-width, max-height * w/h)
   max-height
   (w < min-width) and (h < min-height), where
   (min-width/w ≤ min-height/h) min(max-width, min-height * w/h)
   min-height
   (w < min-width) and (h < min-height), where
   (min-width/w > min-height/h) min-width min(max-height, min-width * h/w)
   (w < min-width) and (h > max-height) min-width max-height
   (w > max-width) and (h < min-height) max-width min-height

   Then apply the rules under "Calculating widths and margins" above, as
   if 'width' were computed as this value.

10.5 Content height: the 'height' property

   'height'

          Value:            <length> | <percentage> | auto | inherit
          Initial:          auto
          Applies to:       all elements but non-replaced inline elements, table
                            columns, and column groups
          Inherited:        no
          Percentages:      see prose
          Media:            visual
          Computed value:   the percentage or 'auto' (see prose under
                            <percentage>) or the absolute length

   This property specifies the content height of boxes.

   This property does not apply to non-replaced inline elements. See the
   section on computing heights and margins for non-replaced inline
   elements for the rules used instead.

   Values have the following meanings:

   <length>
          Specifies the height of the content area using a length value.

   <percentage>
          Specifies a percentage height. The percentage is calculated with
          respect to the height of the generated box's containing block.
          If the height of the containing block is not specified
          explicitly (i.e., it depends on content height), and this
          element is not absolutely positioned, the value computes to
          'auto'. A percentage height on the root element is relative to
          the initial containing block. Note: For absolutely positioned
          elements whose containing block is based on a block-level
          element, the percentage is calculated with respect to the height
          of the padding box of that element. This is a change from CSS1,
          where the percentage was always calculated with respect to the
          content box of the parent element.

   auto
          The height depends on the values of other properties. See the
          prose below.

   Note that the height of the containing block of an absolutely
   positioned element is independent of the size of the element itself,
   and thus a percentage height on such an element can always be resolved.
   However, it may be that the height is not known until elements that
   come later in the document have been processed.

   Negative values for 'height' are illegal.

   Example(s):

   For example, the following rule sets the content height of paragraphs
   to 100 pixels:
p { height: 100px }

   Paragraphs of which the height of the contents exceeds 100 pixels will
   overflow according to the 'overflow' property.

10.6 Calculating heights and margins

   For calculating the values of 'top', 'margin-top', 'height',
   'margin-bottom', and 'bottom' a distinction must be made between
   various kinds of boxes:
    1. inline, non-replaced elements
    2. inline, replaced elements
    3. block-level, non-replaced elements in normal flow
    4. block-level, replaced elements in normal flow
    5. floating, non-replaced elements
    6. floating, replaced elements
    7. absolutely positioned, non-replaced elements
    8. absolutely positioned, replaced elements
    9. 'inline-block', non-replaced elements in normal flow
   10. 'inline-block', replaced elements in normal flow

   For Points 1-6 and 9-10, the used values of 'top' and 'bottom' are
   determined by the rules in section 9.4.3.

   Note: these rules apply to the root element just as to any other
   element.

   Note. The used value of 'height' calculated below is a tentative value,
   and may have to be calculated multiple times, depending on 'min-height'
   and 'max-height', see the section Minimum and maximum heights below.

  10.6.1 Inline, non-replaced elements

   The 'height' property does not apply. The height of the content area
   should be based on the font, but this specification does not specify
   how. A UA may, e.g., use the em-box or the maximum ascender and
   descender of the font. (The latter would ensure that glyphs with parts
   above or below the em-box still fall within the content area, but leads
   to differently sized boxes for different fonts; the former would ensure
   authors can control background styling relative to the 'line-height',
   but leads to glyphs painting outside their content area.)

   Note: level 3 of CSS will probably include a property to select which
   measure of the font is used for the content height.

   The vertical padding, border and margin of an inline, non-replaced box
   start at the top and bottom of the content area, and has nothing to do
   with the 'line-height'. But only the 'line-height' is used when
   calculating the height of the line box.

   If more than one font is used (this could happen when glyphs are found
   in different fonts), the height of the content area is not defined by
   this specification. However, we suggest that the height is chosen such
   that the content area is just high enough for either (1) the em-boxes,
   or (2) the maximum ascenders and descenders, of all the fonts in the
   element. Note that this may be larger than any of the font sizes
   involved, depending on the baseline alignment of the fonts.

  10.6.2 Inline replaced elements, block-level replaced elements in normal flow,
  'inline-block' replaced elements in normal flow and floating replaced elements

   If 'margin-top', or 'margin-bottom' are 'auto', their used value is 0.

   If 'height' and 'width' both have computed values of 'auto' and the
   element also has an intrinsic height, then that intrinsic height is the
   used value of 'height'.

   Otherwise, if 'height' has a computed value of 'auto', and the element
   has an intrinsic ratio then the used value of 'height' is:

     (used width) / (intrinsic ratio)

   Otherwise, if 'height' has a computed value of 'auto', and the element
   has an intrinsic height, then that intrinsic height is the used value
   of 'height'.

   Otherwise, if 'height' has a computed value of 'auto', but none of the
   conditions above are met, then the used value of 'height' must be set
   to the height of the largest rectangle that has a 2:1 ratio, has a
   height not greater than 150px, and has a width not greater than the
   device width.

  10.6.3 Block-level non-replaced elements in normal flow when 'overflow'
  computes to 'visible'

   This section also applies to block-level non-replaced elements in
   normal flow when 'overflow' does not compute to 'visible' but has been
   propagated to the viewport.

   If 'margin-top', or 'margin-bottom' are 'auto', their used value is 0.
   If 'height' is 'auto', the height depends on whether the element has
   any block-level children and whether it has padding or borders:

   The element's height is the distance from its top content edge to the
   first applicable of the following:
    1. the bottom edge of the last line box, if the box establishes a
       inline formatting context with one or more lines
    2. the bottom edge of the bottom (possibly collapsed) margin of its
       last in-flow child, if the child's bottom margin does not collapse
       with the element's bottom margin
    3. the bottom border edge of the last in-flow child whose top margin
       doesn't collapse with the element's bottom margin
    4. zero, otherwise

   Only children in the normal flow are taken into account (i.e., floating
   boxes and absolutely positioned boxes are ignored, and relatively
   positioned boxes are considered without their offset). Note that the
   child box may be an anonymous block box.

  10.6.4 Absolutely positioned, non-replaced elements

   For the purposes of this section and the next, the term "static
   position" (of an element) refers, roughly, to the position an element
   would have had in the normal flow. More precisely, the static position
   for 'top' is the distance from the top edge of the containing block to
   the top margin edge of a hypothetical box that would have been the
   first box of the element if its specified 'position' value had been
   'static' and its specified 'float' had been 'none' and its specified
   'clear' had been 'none'. (Note that due to the rules in section 9.7
   this might require also assuming a different computed value for
   'display'.) The value is negative if the hypothetical box is above the
   containing block.

   But rather than actually calculating the dimensions of that
   hypothetical box, user agents are free to make a guess at its probable
   position.

   For the purposes of calculating the static position, the containing
   block of fixed positioned elements is the initial containing block
   instead of the viewport.

   For absolutely positioned elements, the used values of the vertical
   dimensions must satisfy this constraint:

     'top' + 'margin-top' + 'border-top-width' + 'padding-top' + 'height'
     + 'padding-bottom' + 'border-bottom-width' + 'margin-bottom' +
     'bottom' = height of containing block

   If all three of 'top', 'height', and 'bottom' are auto, set 'top' to
   the static position and apply rule number three below.

   If none of the three are 'auto': If both 'margin-top' and
   'margin-bottom' are 'auto', solve the equation under the extra
   constraint that the two margins get equal values. If one of
   'margin-top' or 'margin-bottom' is 'auto', solve the equation for that
   value. If the values are over-constrained, ignore the value for
   'bottom' and solve for that value.

   Otherwise, pick the one of the following six rules that applies.
    1. 'top' and 'height' are 'auto' and 'bottom' is not 'auto', then the
       height is based on the content per 10.6.7, set 'auto' values for
       'margin-top' and 'margin-bottom' to 0, and solve for 'top'
    2. 'top' and 'bottom' are 'auto' and 'height' is not 'auto', then set
       'top' to the static position, set 'auto' values for 'margin-top'
       and 'margin-bottom' to 0, and solve for 'bottom'
    3. 'height' and 'bottom' are 'auto' and 'top' is not 'auto', then the
       height is based on the content per 10.6.7, set 'auto' values for
       'margin-top' and 'margin-bottom' to 0, and solve for 'bottom'
    4. 'top' is 'auto', 'height' and 'bottom' are not 'auto', then set
       'auto' values for 'margin-top' and 'margin-bottom' to 0, and solve
       for 'top'
    5. 'height' is 'auto', 'top' and 'bottom' are not 'auto', then 'auto'
       values for 'margin-top' and 'margin-bottom' are set to 0 and solve
       for 'height'
    6. 'bottom' is 'auto', 'top' and 'height' are not 'auto', then set
       'auto' values for 'margin-top' and 'margin-bottom' to 0 and solve
       for 'bottom'

  10.6.5 Absolutely positioned, replaced elements

   This situation is similar to the previous one, except that the element
   has an intrinsic height. The sequence of substitutions is now:
    1. The used value of 'height' is determined as for inline replaced
       elements. If 'margin-top' or 'margin-bottom' is specified as 'auto'
       its used value is determined by the rules below.
    2. If both 'top' and 'bottom' have the value 'auto', replace 'top'
       with the element's static position.
    3. If 'bottom' is 'auto', replace any 'auto' on 'margin-top' or
       'margin-bottom' with '0'.
    4. If at this point both 'margin-top' and 'margin-bottom' are still
       'auto', solve the equation under the extra constraint that the two
       margins must get equal values.
    5. If at this point there is only one 'auto' left, solve the equation
       for that value.
    6. If at this point the values are over-constrained, ignore the value
       for 'bottom' and solve for that value.

  10.6.6 Complicated cases

   This section applies to:
     * Block-level, non-replaced elements in normal flow when 'overflow'
       does not compute to 'visible' (except if the 'overflow' property's
       value has been propagated to the viewport).
     * 'Inline-block', non-replaced elements.
     * Floating, non-replaced elements.

   If 'margin-top', or 'margin-bottom' are 'auto', their used value is 0.
   If 'height' is 'auto', the height depends on the element's descendants
   per 10.6.7.

   For 'inline-block' elements, the margin box is used when calculating
   the height of the line box.

  10.6.7 'Auto' heights for block formatting context roots

   In certain cases (see, e.g., sections 10.6.4 and 10.6.6 above), the
   height of an element that establishes a block formatting context is
   computed as follows:

   If it only has inline-level children, the height is the distance
   between the top of the topmost line box and the bottom of the
   bottommost line box.

   If it has block-level children, the height is the distance between the
   top margin-edge of the topmost block-level child box and the bottom
   margin-edge of the bottommost block-level child box.

   Absolutely positioned children are ignored, and relatively positioned
   boxes are considered without their offset. Note that the child box may
   be an anonymous block box.

   In addition, if the element has any floating descendants whose bottom
   margin edge is below the element's bottom content edge, then the height
   is increased to include those edges. Only floats that participate in
   this block formatting context are taken into account, e.g., floats
   inside absolutely positioned descendants or other floats are not.

10.7 Minimum and maximum heights: 'min-height' and 'max-height'

   It is sometimes useful to constrain the height of elements to a certain
   range. Two properties offer this functionality:

   'min-height'

          Value:            <length> | <percentage> | inherit
          Initial:          0
          Applies to:       all elements but non-replaced inline elements, table
                            columns, and column groups
          Inherited:        no
          Percentages:      see prose
          Media:            visual
          Computed value:   the percentage as specified or the absolute length

   'max-height'

         Value:            <length> | <percentage> | none | inherit
         Initial:          none
         Applies to:       all elements but non-replaced inline elements, table
                           columns, and column groups
         Inherited:        no
         Percentages:      see prose
         Media:            visual
         Computed value:   the percentage as specified or the absolute length or
                           'none'

   These two properties allow authors to constrain box heights to a
   certain range. Values have the following meanings:

   <length>
          Specifies a fixed minimum or maximum computed height.

   <percentage>
          Specifies a percentage for determining the used value. The
          percentage is calculated with respect to the height of the
          generated box's containing block. If the height of the
          containing block is not specified explicitly (i.e., it depends
          on content height), and this element is not absolutely
          positioned, the percentage value is treated as '0' (for
          'min-height') or 'none' (for 'max-height').

   none
          (Only on 'max-height') No limit on the height of the box.

   Negative values for 'min-height' and 'max-height' are illegal.

   In CSS 2.1, the effect of 'min-height' and 'max-height' on tables,
   inline tables, table cells, table rows, and row groups is undefined.

   The following algorithm describes how the two properties influence the
   used value of the 'height' property:
    1. The tentative used height is calculated (without 'min-height' and
       'max-height') following the rules under "Calculating heights and
       margins" above.
    2. If this tentative height is greater than 'max-height', the rules
       above are applied again, but this time using the value of
       'max-height' as the computed value for 'height'.
    3. If the resulting height is smaller than 'min-height', the rules
       above are applied again, but this time using the value of
       'min-height' as the computed value for 'height'.

   These steps do not affect the real computed values of the above
   properties. The change of used 'height' has no effect on margin
   collapsing except as specifically required by rules for 'min-height' or
   'max-height' in "Collapsing margins" (8.3.1).

   However, for replaced elements with both 'width' and 'height' computed
   as 'auto', use the algorithm under Minimum and maximum widths above to
   find the used width and height. Then apply the rules under "Computing
   heights and margins" above, using the resulting width and height as if
   they were the computed values.

10.8 Line height calculations: the 'line-height' and 'vertical-align' properties

   As described in the section on inline formatting contexts, user agents
   flow inline-level boxes into a vertical stack of line boxes. The height
   of a line box is determined as follows:
    1. The height of each inline-level box in the line box is calculated.
       For replaced elements, inline-block elements, and inline-table
       elements, this is the height of their margin box; for inline boxes,
       this is their 'line-height'. (See "Calculating heights and margins"
       and the height of inline boxes in "Leading and half-leading".)
    2. The inline-level boxes are aligned vertically according to their
       'vertical-align' property. In case they are aligned 'top' or
       'bottom', they must be aligned so as to minimize the line box
       height. If such boxes are tall enough, there are multiple solutions
       and CSS 2.1 does not define the position of the line box's baseline
       (i.e., the position of the strut, see below).
    3. The line box height is the distance between the uppermost box top
       and the lowermost box bottom. (This includes the strut, as
       explained under 'line-height' below.)

   Empty inline elements generate empty inline boxes, but these boxes
   still have margins, padding, borders and a line height, and thus
   influence these calculations just like elements with content.

  10.8.1 Leading and half-leading

   CSS assumes that every font has font metrics that specify a
   characteristic height above the baseline and a depth below it. In this
   section we use A to mean that height (for a given font at a given size)
   and D the depth. We also define AD = A + D, the distance from the top
   to the bottom. (See the note below for how to find A and D for TrueType
   and OpenType fonts.) Note that these are metrics of the font as a whole
   and need not correspond to the ascender and descender of any individual
   glyph.

   User agent must align the glyphs in a non-replaced inline box to each
   other by their relevant baselines. Then, for each glyph, determine the
   A and D. Note that glyphs in a single element may come from different
   fonts and thus need not all have the same A and D. If the inline box
   contains no glyphs at all, it is considered to contain a strut (an
   invisible glyph of zero width) with the A and D of the element's first
   available font.

   Still for each glyph, determine the leading L to add, where L =
   'line-height' - AD. Half the leading is added above A and the other
   half below D, giving the glyph and its leading a total height above the
   baseline of A' = A + L/2 and a total depth of D' = D + L/2.

   Note. L may be negative.

   The height of the inline box encloses all glyphs and their half-leading
   on each side and is thus exactly 'line-height'. Boxes of child elements
   do not influence this height.

   Although margins, borders, and padding of non-replaced elements do not
   enter into the line box calculation, they are still rendered around
   inline boxes. This means that if the height specified by 'line-height'
   is less than the content height of contained boxes, backgrounds and
   colors of padding and borders may "bleed" into adjoining line boxes.
   User agents should render the boxes in document order. This will cause
   the borders on subsequent lines to paint over the borders and text of
   previous lines.

   Note. CSS 2.1 does not define what the content area of an inline box is
   (see 10.6.1 above) and thus different UAs may draw the backgrounds and
   borders in different places.

   Note. It is recommended that implementations that use OpenType or
   TrueType fonts use the metrics "sTypoAscender" and "sTypoDescender"
   from the font's OS/2 table for A and D (after scaling to the current
   element's font size). In the absence of these metrics, the "Ascent" and
   "Descent" metrics from the HHEA table should be used.

   'line-height'

         Value:            normal | <number> | <length> | <percentage> | inherit
         Initial:          normal
         Applies to:       all elements
         Inherited:        yes
         Percentages:      refer to the font size of the element itself
         Media:            visual
         Computed value:   for <length> and <percentage> the absolute value;
                           otherwise as specified

   On a block container element whose content is composed of inline-level
   elements, 'line-height' specifies the minimal height of line boxes
   within the element. The minimum height consists of a minimum height
   above the baseline and a minimum depth below it, exactly as if each
   line box starts with a zero-width inline box with the element's font
   and line height properties. We call that imaginary box a "strut." (The
   name is inspired by TeX.).

   The height and depth of the font above and below the baseline are
   assumed to be metrics that are contained in the font. (For more
   details, see CSS level 3.)

   On a non-replaced inline element, 'line-height' specifies the height
   that is used in the calculation of the line box height.

   Values for this property have the following meanings:

   normal
          Tells user agents to set the used value to a "reasonable" value
          based on the font of the element. The value has the same meaning
          as <number>. We recommend a used value for 'normal' between 1.0
          to 1.2. The computed value is 'normal'.

   <length>
          The specified length is used in the calculation of the line box
          height. Negative values are illegal.

   <number>
          The used value of the property is this number multiplied by the
          element's font size. Negative values are illegal. The computed
          value is the same as the specified value.

   <percentage>
          The computed value of the property is this percentage multiplied
          by the element's computed font size. Negative values are
          illegal.

   Example(s):

   The three rules in the example below have the same resultant line
   height:
div { line-height: 1.2; font-size: 10pt }     /* number */
div { line-height: 1.2em; font-size: 10pt }   /* length */
div { line-height: 120%; font-size: 10pt }    /* percentage */

   When an element contains text that is rendered in more than one font,
   user agents may determine the 'normal' 'line-height' value according to
   the largest font size.

   Note. When there is only one value of 'line-height' for all inline
   boxes in a block container box and they are all in the same font (and
   there are no replaced elements, inline-block elements, etc.), the above
   will ensure that baselines of successive lines are exactly
   'line-height' apart. This is important when columns of text in
   different fonts have to be aligned, for example in a table.

   'vertical-align'

   Value:            baseline | sub | super | top | text-top | middle | bottom |
                     text-bottom | <percentage> | <length> | inherit
   Initial:          baseline
   Applies to:       inline-level and 'table-cell' elements
   Inherited:        no
   Percentages:      refer to the 'line-height' of the element itself
   Media:            visual
   Computed value:   for <percentage> and <length> the absolute length,
                     otherwise as specified

   This property affects the vertical positioning inside a line box of the
   boxes generated by an inline-level element.

   Note. Values of this property have different meanings in the context of
   tables. Please consult the section on table height algorithms for
   details.

   The following values only have meaning with respect to a parent inline
   element, or to the strut of a parent block container element.

   In the following definitions, for inline non-replaced elements, the box
   used for alignment is the box whose height is the 'line-height'
   (containing the box's glyphs and the half-leading on each side, see
   above). For all other elements, the box used for alignment is the
   margin box.

   baseline
          Align the baseline of the box with the baseline of the parent
          box. If the box does not have a baseline, align the bottom
          margin edge with the parent's baseline.

   middle
          Align the vertical midpoint of the box with the baseline of the
          parent box plus half the x-height of the parent.

   sub
          Lower the baseline of the box to the proper position for
          subscripts of the parent's box. (This value has no effect on the
          font size of the element's text.)

   super
          Raise the baseline of the box to the proper position for
          superscripts of the parent's box. (This value has no effect on
          the font size of the element's text.)

   text-top
          Align the top of the box with the top of the parent's content
          area (see 10.6.1).

   text-bottom
          Align the bottom of the box with the bottom of the parent's
          content area (see 10.6.1).

   <percentage>
          Raise (positive value) or lower (negative value) the box by this
          distance (a percentage of the 'line-height' value). The value
          '0%' means the same as 'baseline'.

   <length>
          Raise (positive value) or lower (negative value) the box by this
          distance. The value '0cm' means the same as 'baseline'.

   The following values align the element relative to the line box. Since
   the element may have children aligned relative to it (which in turn may
   have descendants aligned relative to them), these values use the bounds
   of the aligned subtree. The aligned subtree of an inline element
   contains that element and the aligned subtrees of all children inline
   elements whose computed 'vertical-align' value is not 'top' or
   'bottom'. The top of the aligned subtree is the highest of the tops of
   the boxes in the subtree, and the bottom is analogous.

   top
          Align the top of the aligned subtree with the top of the line
          box.

   bottom
          Align the bottom of the aligned subtree with the bottom of the
          line box.

   The baseline of an 'inline-table' is the baseline of the first row of
   the table.

   The baseline of an 'inline-block' is the baseline of its last line box
   in the normal flow, unless it has either no in-flow line boxes or if
   its 'overflow' property has a computed value other than 'visible', in
   which case the baseline is the bottom margin edge.

                               11 Visual effects

   Contents
     * 11.1 Overflow and clipping
          + 11.1.1 Overflow: the 'overflow' property
          + 11.1.2 Clipping: the 'clip' property
     * 11.2 Visibility: the 'visibility' property

11.1 Overflow and clipping

   Generally, the content of a block box is confined to the content edges
   of the box. In certain cases, a box may overflow, meaning its content
   lies partly or entirely outside of the box, e.g.:
     * A line cannot be broken, causing the line box to be wider than the
       block box.
     * A block-level box is too wide for the containing block. This may
       happen when an element's 'width' property has a value that causes
       the generated block box to spill over sides of the containing
       block.
     * An element's height exceeds an explicit height assigned to the
       containing block (i.e., the containing block's height is determined
       by the 'height' property, not by content height).
     * A descendant box is positioned absolutely, partly outside the box.
       Such boxes are not always clipped by the overflow property on their
       ancestors; specifically, they are not clipped by the overflow of
       any ancestor between themselves and their containing block
     * A descendant box has negative margins, causing it to be positioned
       partly outside the box.
     * The 'text-indent' property causes an inline box to hang off either
       the left or right edge of the block box.

   Whenever overflow occurs, the 'overflow' property specifies whether a
   box is clipped to its padding edge, and if so, whether a scrolling
   mechanism is provided to access any clipped out content.

  11.1.1 Overflow: the 'overflow' property

   'overflow'

          Value:            visible | hidden | scroll | auto | inherit
          Initial:          visible
          Applies to:       block containers
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property specifies whether content of a block container element is
   clipped when it overflows the element's box. It affects the clipping of
   all of the element's content except any descendant elements (and their
   respective content and descendants) whose containing block is the
   viewport or an ancestor of the element. Values have the following
   meanings:

   visible
          This value indicates that content is not clipped, i.e., it may
          be rendered outside the block box.

   hidden
          This value indicates that the content is clipped and that no
          scrolling user interface should be provided to view the content
          outside the clipping region.

   scroll
          This value indicates that the content is clipped and that if the
          user agent uses a scrolling mechanism that is visible on the
          screen (such as a scroll bar or a panner), that mechanism should
          be displayed for a box whether or not any of its content is
          clipped. This avoids any problem with scrollbars appearing and
          disappearing in a dynamic environment. When this value is
          specified and the target medium is 'print', overflowing content
          may be printed.

   auto
          The behavior of the 'auto' value is user agent-dependent, but
          should cause a scrolling mechanism to be provided for
          overflowing boxes.

   Even if 'overflow' is set to 'visible', content may be clipped to a
   UA's document window by the native operating environment.

   UAs must apply the 'overflow' property set on the root element to the
   viewport. When the root element is an HTML "HTML" element or an XHTML
   "html" element, and that element has an HTML "BODY" element or an XHTML
   "body" element as a child, user agents must instead apply the
   'overflow' property from the first such child element to the viewport,
   if the value on the root element is 'visible'. The 'visible' value when
   used for the viewport must be interpreted as 'auto'. The element from
   which the value is propagated must have a used value for 'overflow' of
   'visible'.

   In the case of a scrollbar being placed on an edge of the element's
   box, it should be inserted between the inner border edge and the outer
   padding edge. Any space taken up by the scrollbars should be taken out
   of (subtracted from the dimensions of) the containing block formed by
   the element with the scrollbars.

   Example(s):

   Consider the following example of a block quotation (<blockquote>) that
   is too big for its containing block (established by a <div>). Here is
   the source:
<div>
<blockquote>
<p>I didn't like the play, but then I saw
it under adverse conditions - the curtain was up.</p>
<cite>- Groucho Marx</cite>
</blockquote>
</div>

   Here is the style sheet controlling the sizes and style of the
   generated boxes:
div { width : 100px; height: 100px;
      border: thin solid red;
      }

blockquote   { width : 125px; height : 100px;
      margin-top: 50px; margin-left: 50px;
      border: thin dashed black
      }

cite { display: block;
       text-align : right;
       border: none
       }

   The initial value of 'overflow' is 'visible', so the <blockquote> would
   be formatted without clipping, something like this:

   Rendered overflow    [D]

   Setting 'overflow' to 'hidden' for the <div>, on the other hand, causes
   the <blockquote> to be clipped by the containing <div>:

   Clipped overflow    [D]

   A value of 'scroll' would tell UAs that support a visible scrolling
   mechanism to display one so that users could access the clipped
   content.

   Finally, consider this case where an absolutely positioned element is
   mixed with an overflow parent.

   Style sheet:
  container { position: relative; border: solid; }
  scroller { overflow: scroll; height: 5em; margin: 5em; }
  satellite { position: absolute; top: 0; }
  body { height: 10em; }

   Document fragment:
  <container>
   <scroller>
    <satellite/>
    <body/>
   </scroller>
  </container>

   In this example, the "scroller" element will not scroll the "satellite"
   element, because the latter's containing block is outside the element
   whose overflow is being clipped and scrolled.

  11.1.2 Clipping: the 'clip' property

   A clipping region defines what portion of an element's border box is
   visible. By default, the element is not clipped. However, the clipping
   region may be explicitly set with the 'clip' property.

   'clip'

   Value:   <shape> | auto | inherit
   Initial:   auto
   Applies to:   absolutely positioned elements
   Inherited:   no
   Percentages:   N/A
   Media:   visual
   Computed value:   'auto' if specified as 'auto', otherwise a rectangle
   with four values, each of which is 'auto' if specified as 'auto' and
   the computed length otherwise

   The 'clip' property applies only to absolutely positioned elements.
   Values have the following meanings:

   auto
          The element does not clip.

   <shape>
          In CSS 2.1, the only valid <shape> value is: rect(<top>,
          <right>, <bottom>, <left>) where <top> and <bottom> specify
          offsets from the top border edge of the box, and <right>, and
          <left> specify offsets from the left border edge of the box.
          Authors should separate offset values with commas. User agents
          must support separation with commas, but may also support
          separation without commas (but not a combination), because a
          previous revision of this specification was ambiguous in this
          respect.

          <top>, <right>, <bottom>, and <left> may either have a <length>
          value or 'auto'. Negative lengths are permitted. The value
          'auto' means that a given edge of the clipping region will be
          the same as the edge of the element's generated border box
          (i.e., 'auto' means the same as '0' for <top> and <left>, the
          same as the used value of the height plus the sum of vertical
          padding and border widths for <bottom>, and the same as the used
          value of the width plus the sum of the horizontal padding and
          border widths for <right>, such that four 'auto' values result
          in the clipping region being the same as the element's border
          box).

          When coordinates are rounded to pixel coordinates, care should
          be taken that no pixels remain visible when <left> and <right>
          have the same value (or <top> and <bottom> have the same value),
          and conversely that no pixels within the element's border box
          remain hidden when these values are 'auto'.

   An element's clipping region clips out any aspect of the element (e.g.,
   content, children, background, borders, text decoration, outline and
   visible scrolling mechanism — if any) that is outside the clipping
   region. Content that has been clipped does not cause overflow.

   The element's ancestors may also clip portions of their content (e.g.,
   via their own 'clip' property and/or if their 'overflow' property is
   not 'visible'); what is rendered is the cumulative intersection.

   If the clipping region exceeds the bounds of the UA's document window,
   content may be clipped to that window by the native operating
   environment.

   Example(s):

   Example: The following two rules:
p#one { clip: rect(5px, 40px, 45px, 5px); }
p#two { clip: rect(5px, 55px, 45px, 5px); }

   and assuming both Ps are 50 by 55 px, will create, respectively, the
   rectangular clipping regions delimited by the dashed lines in the
   following illustrations:

   Two clipping regions    [D]

   Note. In CSS 2.1, all clipping regions are rectangular. We anticipate
   future extensions to permit non-rectangular clipping. Future updates
   may also reintroduce a syntax for offsetting shapes from each edge
   instead of offsetting from a point.

11.2 Visibility: the 'visibility' property

   'visibility'

          Value:            visible | hidden | collapse | inherit
          Initial:          visible
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   The 'visibility' property specifies whether the boxes generated by an
   element are rendered. Invisible boxes still affect layout (set the
   'display' property to 'none' to suppress box generation altogether).
   Values have the following meanings:

   visible
          The generated box is visible.

   hidden
          The generated box is invisible (fully transparent, nothing is
          drawn), but still affects layout. Furthermore, descendants of
          the element will be visible if they have 'visibility: visible'.

   collapse
          Please consult the section on dynamic row and column effects in
          tables. If used on elements other than rows, row groups,
          columns, or column groups, 'collapse' has the same meaning as
          'hidden'.

   This property may be used in conjunction with scripts to create dynamic
   effects.

   In the following example, pressing either form button invokes an
   author-defined script function that causes the corresponding box to
   become visible and the other to be hidden. Since these boxes have the
   same size and position, the effect is that one replaces the other. (The
   script code is in a hypothetical script language. It may or may not
   have any effect in a CSS-capable UA.)
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
<HEAD><TITLE>Dynamic visibility example</TITLE>
<META
 http-equiv="Content-Script-Type"
 content="application/x-hypothetical-scripting-language">
<STYLE type="text/css">
<!--
   #container1 { position: absolute;
                 top: 2in; left: 2in; width: 2in }
   #container2 { position: absolute;
                 top: 2in; left: 2in; width: 2in;
                 visibility: hidden; }
-->
</STYLE>
</HEAD>
<BODY>
<P>Choose a suspect:</P>
<DIV id="container1">
   <IMG alt="Al Capone"
        width="100" height="100"
        src="suspect1.png">
   <P>Name: Al Capone</P>
   <P>Residence: Chicago</P>
</DIV>

<DIV id="container2">
   <IMG alt="Lucky Luciano"
        width="100" height="100"
        src="suspect2.png">
   <P>Name: Lucky Luciano</P>
   <P>Residence: New York</P>
</DIV>

<FORM method="post"
      action="http://www.suspect.org/process-bums">
   <P>
   <INPUT name="Capone" type="button"
          value="Capone"
          onclick='show("container1");hide("container2")'>
   <INPUT name="Luciano" type="button"
          value="Luciano"
          onclick='show("container2");hide("container1")'>
</FORM>
</BODY>
</HTML>

              12 Generated content, automatic numbering, and lists

   Contents
     * 12.1 The :before and :after pseudo-elements
     * 12.2 The 'content' property
     * 12.3 Quotation marks
          + 12.3.1 Specifying quotes with the 'quotes' property
          + 12.3.2 Inserting quotes with the 'content' property
     * 12.4 Automatic counters and numbering
          + 12.4.1 Nested counters and scope
          + 12.4.2 Counter styles
          + 12.4.3 Counters in elements with 'display: none'
     * 12.5 Lists
          + 12.5.1 Lists: the 'list-style-type', 'list-style-image',
            'list-style-position', and 'list-style' properties

   In some cases, authors may want user agents to render content that does
   not come from the document tree. One familiar example of this is a
   numbered list; the author does not want to list the numbers explicitly,
   he or she wants the user agent to generate them automatically.
   Similarly, authors may want the user agent to insert the word "Figure"
   before the caption of a figure, or "Chapter 7" before the seventh
   chapter title. For audio or braille in particular, user agents should
   be able to insert these strings.

   In CSS 2.1, content may be generated by two mechanisms:
     * The 'content' property, in conjunction with the :before and :after
       pseudo-elements.
     * Elements with a value of 'list-item' for the 'display' property.

12.1 The :before and :after pseudo-elements

   Authors specify the style and location of generated content with the
   :before and :after pseudo-elements. As their names indicate, the
   :before and :after pseudo-elements specify the location of content
   before and after an element's document tree content. The 'content'
   property, in conjunction with these pseudo-elements, specifies what is
   inserted.

   Example(s):

   For example, the following rule inserts the string "Note: " before the
   content of every P element whose "class" attribute has the value
   "note":
p.note:before { content: "Note: " }

   The formatting objects (e.g., boxes) generated by an element include
   generated content. So, for example, changing the above style sheet to:
p.note:before { content: "Note: " }
p.note        { border: solid green }

   would cause a solid green border to be rendered around the entire
   paragraph, including the initial string.

   The :before and :after pseudo-elements inherit any inheritable
   properties from the element in the document tree to which they are
   attached.

   Example(s):

   For example, the following rules insert an open quote mark before every
   Q element. The color of the quote mark will be red, but the font will
   be the same as the font of the rest of the Q element:
q:before {
  content: open-quote;
  color: red
}

   In a :before or :after pseudo-element declaration, non-inherited
   properties take their initial values.

   Example(s):

   So, for example, because the initial value of the 'display' property is
   'inline', the quote in the previous example is inserted as an inline
   box (i.e., on the same line as the element's initial text content). The
   next example explicitly sets the 'display' property to 'block', so that
   the inserted text becomes a block:
body:after {
    content: "The End";
    display: block;
    margin-top: 2em;
    text-align: center;
}

   The :before and :after pseudo-elements interact with other boxes as if
   they were real elements inserted just inside their associated element.

   Example(s):

   For example, the following document fragment and style sheet:
<p> Text </p>                   p:before { display: block; content: 'Some'; }

   ...would render in exactly the same way as the following document
   fragment and style sheet:
<p><span>Some</span> Text </p>  span { display: block }

   Similarly, the following document fragment and style sheet:
<h2> Header </h2>     h2:after { display: block; content: 'Thing'; }

   ...would render in exactly the same way as the following document
   fragment and style sheet:
<h2> Header <span>Thing</span></h2>   h2 { display: block; }
                                      span { display: block; }

   Note. This specification does not fully define the interaction of
   :before and :after with replaced elements (such as IMG in HTML). This
   will be defined in more detail in a future specification.

12.2 The 'content' property

   'content'

   Value:   normal | none | [ <string> | <uri> | <counter> |
   attr(<identifier>) | open-quote | close-quote | no-open-quote |
   no-close-quote ]+ | inherit
   Initial:   normal
   Applies to:   :before and :after pseudo-elements
   Inherited:   no
   Percentages:   N/A
   Media:   all
   Computed value:   On elements, always computes to 'normal'. On :before
   and :after, if 'normal' is specified, computes to 'none'. Otherwise,
   for URI values, the absolute URI; for attr() values, the resulting
   string; for other keywords, as specified.

   This property is used with the :before and :after pseudo-elements to
   generate content in a document. Values have the following meanings:

   none
          The pseudo-element is not generated.

   normal
          Computes to 'none' for the :before and :after pseudo-elements.

   <string>
          Text content (see the section on strings).

   <uri>
          The value is a URI that designates an external resource (such as
          an image). If the user agent cannot display the resource it must
          either leave it out as if it were not specified or display some
          indication that the resource cannot be displayed.

   <counter>
          Counters may be specified with two different functions:
          'counter()' or 'counters()'. The former has two forms:
          'counter(name)' or 'counter(name, style)'. The generated text is
          the value of the innermost counter of the given name in scope at
          this pseudo-element; it is formatted in the indicated style
          ('decimal' by default). The latter function also has two forms:
          'counters(name, string)' or 'counters(name, string, style)'. The
          generated text is the value of all counters with the given name
          in scope at this pseudo-element, from outermost to innermost
          separated by the specified string. The counters are rendered in
          the indicated style ('decimal' by default). See the section on
          automatic counters and numbering for more information. The name
          must not be 'none', 'inherit' or 'initial'. Such a name causes
          the declaration to be ignored.

   open-quote and close-quote
          These values are replaced by the appropriate string from the
          'quotes' property.

   no-open-quote and no-close-quote
          Introduces no content, but increments (decrements) the level of
          nesting for quotes.

   attr(X)
          This function returns as a string the value of attribute X for
          the subject of the selector. The string is not parsed by the CSS
          processor. If the subject of the selector does not have an
          attribute X, an empty string is returned. The case-sensitivity
          of attribute names depends on the document language.

   Note. In CSS 2.1, it is not possible to refer to attribute values for
   other elements than the subject of the selector.

   The 'display' property controls whether the content is placed in a
   block or inline box.

   Example(s):

   The following rule causes the string "Chapter: " to be generated before
   each H1 element:
H1:before {
  content: "Chapter: ";
  display: inline;
}

   Authors may include newlines in the generated content by writing the
   "\A" escape sequence in one of the strings after the 'content'
   property. This inserted line break is still subject to the
   'white-space' property. See "Strings" and "Characters and case" for
   more information on the "\A" escape sequence.

   Example(s):

h1:before {
    display: block;
    text-align: center;
    white-space: pre;
    content: "chapter\A hoofdstuk\A chapitre"
}

   Generated content does not alter the document tree. In particular, it
   is not fed back to the document language processor (e.g., for
   reparsing).

12.3 Quotation marks

   In CSS 2.1, authors may specify, in a style-sensitive and
   context-dependent manner, how user agents should render quotation
   marks. The 'quotes' property specifies pairs of quotation marks for
   each level of embedded quotation. The 'content' property gives access
   to those quotation marks and causes them to be inserted before and
   after a quotation.

  12.3.1 Specifying quotes with the 'quotes' property

   'quotes'

          Value:            [<string> <string>]+ | none | inherit
          Initial:          depends on user agent
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property specifies quotation marks for any number of embedded
   quotations. Values have the following meanings:

   none
          The 'open-quote' and 'close-quote' values of the 'content'
          property produce no quotation marks.

   [<string>  <string>]+
          Values for the 'open-quote' and 'close-quote' values of the
          'content' property are taken from this list of pairs of
          quotation marks (opening and closing). The first (leftmost) pair
          represents the outermost level of quotation, the second pair the
          first level of embedding, etc. The user agent must apply the
          appropriate pair of quotation marks according to the level of
          embedding.

   Example(s):

   For example, applying the following style sheet:
/* Specify pairs of quotes for two levels in two languages */
q:lang(en) { quotes: '"' '"' "'" "'" }
q:lang(no) { quotes: "«" "»" '"' '"' }

/* Insert quotes before and after Q element content */
q:before { content: open-quote }
q:after  { content: close-quote }

   to the following HTML fragment:
<HTML lang="en">
  <HEAD>
  <TITLE>Quotes</TITLE>
  </HEAD>
  <BODY>
    <P><Q>Quote me!</Q>
  </BODY>
</HTML>

   would allow a user agent to produce:
"Quote me!"

   while this HTML fragment:
<HTML lang="no">
  <HEAD>
  <TITLE>Quotes</TITLE>
  </HEAD>
  <BODY>
    <P><Q>Trøndere gråter når <Q>Vinsjan på kaia</Q> blir deklamert.</Q>
  </BODY>
</HTML>

   would produce:
«Trøndere gråter når "Vinsjan på kaia" blir deklamert.»

   Note. While the quotation marks specified by 'quotes' in the previous
   examples are conveniently located on computer keyboards, high quality
   typesetting would require different ISO 10646 characters. The following
   informative table lists some of the ISO 10646 quotation mark
   characters:
   Character Approximate rendering ISO 10646 code (hex) Description
   " " 0022 QUOTATION MARK [the ASCII double quotation mark]
   ' ' 0027 APOSTROPHE [the ASCII single quotation mark]
   ‹ < 2039 SINGLE LEFT-POINTING ANGLE QUOTATION MARK
   › > 203A SINGLE RIGHT-POINTING ANGLE QUOTATION MARK
   « « 00AB LEFT-POINTING DOUBLE ANGLE QUOTATION MARK
   » » 00BB RIGHT-POINTING DOUBLE ANGLE QUOTATION MARK
   ‘ ` 2018 LEFT SINGLE QUOTATION MARK [single high-6]
   ’ ' 2019 RIGHT SINGLE QUOTATION MARK [single high-9]
   “ `` 201C LEFT DOUBLE QUOTATION MARK [double high-6]
   ” '' 201D RIGHT DOUBLE QUOTATION MARK [double high-9]
   „ ,, 201E DOUBLE LOW-9 QUOTATION MARK [double low-9]

  12.3.2 Inserting quotes with the 'content' property

   Quotation marks are inserted in appropriate places in a document with
   the 'open-quote' and 'close-quote' values of the 'content' property.
   Each occurrence of 'open-quote' or 'close-quote' is replaced by one of
   the strings from the value of 'quotes', based on the depth of nesting.

   'Open-quote' refers to the first of a pair of quotes, 'close-quote'
   refers to the second. Which pair of quotes is used depends on the
   nesting level of quotes: the number of occurrences of 'open-quote' in
   all generated text before the current occurrence, minus the number of
   occurrences of 'close-quote'. If the depth is 0, the first pair is
   used, if the depth is 1, the second pair is used, etc. If the depth is
   greater than the number of pairs, the last pair is repeated. A
   'close-quote' or 'no-close-quote' that would make the depth negative is
   in error and is ignored (at rendering time): the depth stays at 0 and
   no quote mark is rendered (although the rest of the 'content'
   property's value is still inserted).

   Note. The quoting depth is independent of the nesting of the source
   document or the formatting structure.

   Some typographic styles require open quotation marks to be repeated
   before every paragraph of a quote spanning several paragraphs, but only
   the last paragraph ends with a closing quotation mark. In CSS, this can
   be achieved by inserting "phantom" closing quotes. The keyword
   'no-close-quote' decrements the quoting level, but does not insert a
   quotation mark.

   Example(s):

   The following style sheet puts opening quotation marks on every
   paragraph in a BLOCKQUOTE, and inserts a single closing quote at the
   end:
blockquote p:before     { content: open-quote }
blockquote p:after      { content: no-close-quote }
blockquote p.last:after { content: close-quote }

   This relies on the last paragraph being marked with a class "last".

   For symmetry, there is also a 'no-open-quote' keyword, which inserts
   nothing, but increments the quotation depth by one.

12.4 Automatic counters and numbering

   Automatic numbering in CSS 2.1 is controlled with two properties,
   'counter-increment' and 'counter-reset'. The counters defined by these
   properties are used with the counter() and counters() functions of the
   the 'content' property.

   'counter-reset'

          Value:            [ <identifier> <integer>? ]+ | none | inherit
          Initial:          none
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            all
          Computed value:   as specified

   'counter-increment'

          Value:            [ <identifier> <integer>? ]+ | none | inherit
          Initial:          none
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            all
          Computed value:   as specified

   The 'counter-increment' property accepts one or more names of counters
   (identifiers), each one optionally followed by an integer. The integer
   indicates by how much the counter is incremented for every occurrence
   of the element. The default increment is 1. Zero and negative integers
   are allowed.

   The 'counter-reset' property also contains a list of one or more names
   of counters, each one optionally followed by an integer. The integer
   gives the value that the counter is set to on each occurrence of the
   element. The default is 0.

   The keywords 'none', 'inherit' and 'initial' must not be used as
   counter names. A value of 'none' on its own means no counters are
   reset, resp. incremented. 'Inherit' on its own has its usual meaning
   (see 6.2.1). 'Initial' is reserved for future use.

   Example(s):

   This example shows a way to number chapters and sections with "Chapter
   1", "1.1", "1.2", etc.
BODY {
    counter-reset: chapter;      /* Create a chapter counter scope */
}
H1:before {
    content: "Chapter " counter(chapter) ". ";
    counter-increment: chapter;  /* Add 1 to chapter */
}
H1 {
    counter-reset: section;      /* Set section to 0 */
}
H2:before {
    content: counter(chapter) "." counter(section) " ";
    counter-increment: section;
}

   If an element increments/resets a counter and also uses it (in the
   'content' property of its :before or :after pseudo-element), the
   counter is used after being incremented/reset.

   If an element both resets and increments a counter, the counter is
   reset first and then incremented.

   If the same counter is specified more than once in the value of the
   'counter-reset' and 'counter-increment' properties, each
   reset/increment of the counter is processed in the order specified.

   Example(s):

   The following example will reset the 'section' counter to 0:
H1 { counter-reset: section 2 section }

   The following example will increment the 'chapter' counter by 3:
H1 { counter-increment: chapter chapter 2 }

   The 'counter-reset' property follows the cascading rules. Thus, due to
   cascading, the following style sheet:
H1 { counter-reset: section -1 }
H1 { counter-reset: imagenum 99 }

   will only reset 'imagenum'. To reset both counters, they have to be
   specified together:
H1 { counter-reset: section -1 imagenum 99 }

  12.4.1 Nested counters and scope

   Counters are "self-nesting", in the sense that resetting a counter in a
   descendant element or pseudo-element automatically creates a new
   instance of the counter. This is important for situations like lists in
   HTML, where elements can be nested inside themselves to arbitrary
   depth. It would be impossible to define uniquely named counters for
   each level.

   Example(s):

   Thus, the following suffices to number nested list items. The result is
   very similar to that of setting 'display:list-item' and 'list-style:
   inside' on the LI element:
OL { counter-reset: item }
LI { display: block }
LI:before { content: counter(item) ". "; counter-increment: item }

   The scope of a counter starts at the first element in the document that
   has a 'counter-reset' for that counter and includes the element's
   descendants and its following siblings with their descendants. However,
   it does not include any elements in the scope of a counter with the
   same name created by a 'counter-reset' on a later sibling of the
   element or by a later 'counter-reset' on the same element.

   If 'counter-increment' or 'content' on an element or pseudo-element
   refers to a counter that is not in the scope of any 'counter-reset',
   implementations should behave as though a 'counter-reset' had reset the
   counter to 0 on that element or pseudo-element.

   In the example above, an OL will create a counter, and all children of
   the OL will refer to that counter.

   If we denote by item[n] the n^th instance of the "item" counter, and by
   "{" and "}" the beginning and end of a scope, then the following HTML
   fragment will use the indicated counters. (We assume the style sheet as
   given in the example above).
<OL>                    <!-- {item[0]=0        -->
  <LI>item</LI>         <!--  item[0]++ (=1)   -->
  <LI>item              <!--  item[0]++ (=2)   -->
    <OL>                <!--  {item[1]=0       -->
      <LI>item</LI>     <!--   item[1]++ (=1)  -->
      <LI>item</LI>     <!--   item[1]++ (=2)  -->
      <LI>item          <!--   item[1]++ (=3)  -->
        <OL>            <!--   {item[2]=0      -->
          <LI>item</LI> <!--    item[2]++ (=1) -->
        </OL>           <!--                   -->
        <OL>            <!--   }{item[2]=0     -->
          <LI>item</LI> <!--    item[2]++ (=1) -->
        </OL>           <!--                   -->
      </LI>             <!--   }               -->
      <LI>item</LI>     <!--   item[1]++ (=4)  -->
    </OL>               <!--                   -->
  </LI>                 <!--  }                -->
  <LI>item</LI>         <!--  item[0]++ (=3)   -->
  <LI>item</LI>         <!--  item[0]++ (=4)   -->
</OL>                   <!--                   -->
<OL>                    <!-- }{item[0]=0       -->
  <LI>item</LI>         <!--  item[0]++ (=1)   -->
  <LI>item</LI>         <!--  item[0]++ (=2)   -->
</OL>                   <!--                   -->

   Example(s):

   Another example, showing how scope works when counters are used on
   elements that are not nested, is the following. This shows how the
   style rules given above to number chapters and sections would apply to
   the markup given.
                     <!--"chapter" counter|"section" counter -->
<body>               <!-- {chapter=0      |                  -->
  <h1>About CSS</h1> <!--  chapter++ (=1) | {section=0       -->
  <h2>CSS 2</h2>     <!--                 |  section++ (=1)  -->
  <h2>CSS 2.1</h2>   <!--                 |  section++ (=2)  -->
  <h1>Style</h1>     <!--  chapter++ (=2) |}{ section=0      -->
</body>              <!--                 | }                -->

   The 'counters()' function generates a string composed of all of the
   counters with the same name that are in scope, separated by a given
   string.

   Example(s):

   The following style sheet numbers nested list items as "1", "1.1",
   "1.1.1", etc.
OL { counter-reset: item }
LI { display: block }
LI:before { content: counters(item, ".") " "; counter-increment: item }

  12.4.2 Counter styles

   By default, counters are formatted with decimal numbers, but all the
   styles available for the 'list-style-type' property are also available
   for counters. The notation is:
counter(name)

   for the default style, or:
counter(name, <'list-style-type'>)

   All the styles are allowed, including 'disc', 'circle', 'square', and
   'none'.

   Example(s):

H1:before        { content: counter(chno, upper-latin) ". " }
H2:before        { content: counter(section, upper-roman) " - " }
BLOCKQUOTE:after { content: " [" counter(bq, lower-greek) "]" }
DIV.note:before  { content: counter(notecntr, disc) " " }
P:before         { content: counter(p, none) }

  12.4.3 Counters in elements with 'display: none'

   An element that is not displayed ('display' set to 'none') cannot
   increment or reset a counter.

   Example(s):

   For example, with the following style sheet, H2s with class "secret" do
   not increment 'count2'.
H2.secret {counter-increment: count2; display: none}

   Pseudo-elements that are not generated also cannot increment or reset a
   counter.

   Example(s):

   For example, the following does not increment 'heading':
h1::before {
    content: normal;
    counter-increment: heading;
}

   Elements with 'visibility' set to 'hidden', on the other hand, do
   increment counters.

12.5 Lists

   CSS 2.1 offers basic visual formatting of lists. An element with
   'display: list-item' generates a principal block box for the element's
   content and, depending on the values of 'list-style-type' and
   'list-style-image', possibly also a marker box as a visual indication
   that the element is a list item.

   The list properties describe basic visual formatting of lists: they
   allow style sheets to specify the marker type (image, glyph, or
   number), and the marker position with respect to the principal box
   (outside it or within it before content). They do not allow authors to
   specify distinct style (colors, fonts, alignment, etc.) for the list
   marker or adjust its position with respect to the principal box; these
   may be derived from the principal box.

   The background properties apply to the principal box only; an 'outside'
   marker box is transparent.

  12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   'list-style-type'

   Value:   disc | circle | square | decimal | decimal-leading-zero |
   lower-roman | upper-roman | lower-greek | lower-latin | upper-latin |
   armenian | georgian | lower-alpha | upper-alpha | none | inherit
   Initial:   disc
   Applies to:   elements with 'display: list-item'
   Inherited:   yes
   Percentages:   N/A
   Media:   visual
   Computed value:   as specified

   This property specifies appearance of the list item marker if
   'list-style-image' has the value 'none' or if the image pointed to by
   the URI cannot be displayed. The value 'none' specifies no marker,
   otherwise there are three types of marker: glyphs, numbering systems,
   and alphabetic systems.

   Glyphs are specified with disc, circle, and square. Their exact
   rendering depends on the user agent.

   Numbering systems are specified with:

   decimal
          Decimal numbers, beginning with 1.

   decimal-leading-zero
          Decimal numbers padded by initial zeros (e.g., 01, 02, 03, ...,
          98, 99).

   lower-roman
          Lowercase roman numerals (i, ii, iii, iv, v, etc.).

   upper-roman
          Uppercase roman numerals (I, II, III, IV, V, etc.).

   georgian
          Traditional Georgian numbering (an, ban, gan, ..., he, tan, in,
          in-an, ...).

   armenian
          Traditional uppercase Armenian numbering.

   Alphabetic systems are specified with:

   lower-latin or lower-alpha
          Lowercase ascii letters (a, b, c, ... z).

   upper-latin or upper-alpha
          Uppercase ascii letters (A, B, C, ... Z).

   lower-greek
          Lowercase classical Greek alpha, beta, gamma, ... (α, β, γ, ...)

   This specification does not define how alphabetic systems wrap at the
   end of the alphabet. For instance, after 26 list items, 'lower-latin'
   rendering is undefined. Therefore, for long lists, we recommend that
   authors specify true numbers.

   CSS 2.1 does not define how the list numbering is reset and
   incremented. This is expected to be defined in the CSS List Module
   [CSS3LIST].

   For example, the following HTML document:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
   <HEAD>
     <TITLE>Lowercase latin numbering</TITLE>
     <STYLE type="text/css">
          ol { list-style-type: lower-roman }
     </STYLE>
  </HEAD>
  <BODY>
    <OL>
      <LI> This is the first item.
      <LI> This is the second item.
      <LI> This is the third item.
    </OL>
  </BODY>
</HTML>

   might produce something like this:
  i This is the first item.
 ii This is the second item.
iii This is the third item.

   The list marker alignment (here, right justified) depends on the user
   agent.

   'list-style-image'

          Value:            <uri> | none | inherit
          Initial:          none
          Applies to:       elements with 'display: list-item'
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   absolute URI or 'none'

   This property sets the image that will be used as the list item marker.
   When the image is available, it will replace the marker set with the
   'list-style-type' marker.

   The size of the image is calculated from the following rules:
    1. If the image has a intrinsic width and height, the used width and
       height are the intrinsic width and height.
    2. Otherwise, if the image has an intrinsic ratio and either an
       intrinsic width or an intrinsic height, the used width/height is
       the same as the provided intrinsic width/height, and the used value
       of the missing dimension is calculated from the provided dimension
       and the ratio.
    3. Otherwise, if the image has an intrinsic ratio, the used width is
       1em and the used height is calculated from this width and the
       intrinsic ratio. If this would produce a height larger than 1em,
       then the used height is instead set to 1em and the used width is
       calculated from this height and the intrinsic ratio.
    4. Otherwise, the image's used width is its intrinsic width if it has
       one, or else 1em. The image's used height is its intrinsic height
       if it has one, or else 1em.

   Example(s):

   The following example sets the marker at the beginning of each list
   item to be the image "ellipse.png".
ul { list-style-image: url("http://png.com/ellipse.png") }

   'list-style-position'

          Value:            inside | outside | inherit
          Initial:          outside
          Applies to:       elements with 'display: list-item'
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property specifies the position of the marker box with respect to
   the principal block box. Values have the following meanings:

   outside
          The marker box is outside the principal block box. The position
          of the list-item marker adjacent to floats is undefined in
          CSS 2.1. CSS 2.1 does not specify the precise location of the
          marker box or its position in the painting order, but does
          require that for list items whose 'direction' property is 'ltr'
          the marker box be on the left side of the content and for
          elements whose 'direction' property is 'rtl' the marker box be
          on the right side of the content. The marker box is fixed with
          respect to the principal block box's border and does not scroll
          with the principal block box's content. In CSS 2.1, a UA may
          hide the marker if the element's 'overflow' is other than
          'visible'. (This is expected to change in the future.) The size
          or contents of the marker box may affect the height of the
          principal block box and/or the height of its first line box, and
          in some cases may cause the creation of a new line box. Note:
          This interaction may be more precisely defined in a future level
          of CSS.

   inside
          The marker box is placed as the first inline box in the
          principal block box, before the element's content and before any
          :before pseudo-elements. CSS 2.1 does not specify the precise
          location of the marker box.

   For example:
<HTML>
  <HEAD>
    <TITLE>Comparison of inside/outside position</TITLE>
    <STYLE type="text/css">
      ul         { list-style: outside }
      ul.compact { list-style: inside }
    </STYLE>
  </HEAD>
  <BODY>
    <UL>
      <LI>first list item comes first
      <LI>second list item comes second
    </UL>

    <UL class="compact">
      <LI>first list item comes first
      <LI>second list item comes second
    </UL>
  </BODY>
</HTML>

   The above example may be formatted as:

   Difference between inside and outside list style position    [D]

   In right-to-left text, the markers would have been on the right side of
   the box.

   'list-style'

          Value:            [ <'list-style-type'> || <'list-style-position'> ||
                            <'list-style-image'> ] | inherit
          Initial:          see individual properties
          Applies to:       elements with 'display: list-item'
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   see individual properties

   The 'list-style' property is a shorthand notation for setting the three
   properties 'list-style-type', 'list-style-image', and
   'list-style-position' at the same place in the style sheet.

   Example(s):

ul { list-style: upper-roman inside }  /* Any "ul" element */
ul > li > ul { list-style: circle outside } /* Any "ul" child
                                             of an "li" child
                                             of a "ul" element */

   Although authors may specify 'list-style' information directly on list
   item elements (e.g., "li" in HTML), they should do so with care. The
   following rules look similar, but the first declares a descendant
   selector and the second a (more specific) child selector.
ol.alpha li   { list-style: lower-alpha } /* Any "li" descendant of an "ol" */
ol.alpha > li { list-style: lower-alpha } /* Any "li" child of an "ol" */

   Authors who use only the descendant selector may not achieve the
   results they expect. Consider the following rules:
<HTML>
  <HEAD>
    <TITLE>WARNING: Unexpected results due to cascade</TITLE>
    <STYLE type="text/css">
      ol.alpha li  { list-style: lower-alpha }
      ul li        { list-style: disc }
    </STYLE>
  </HEAD>
  <BODY>
    <OL class="alpha">
      <LI>level 1
      <UL>
         <LI>level 2
      </UL>
    </OL>
  </BODY>
</HTML>

   The desired rendering would have level 1 list items with 'lower-alpha'
   labels and level 2 items with 'disc' labels. However, the cascading
   order will cause the first style rule (which includes specific class
   information) to mask the second. The following rules solve the problem
   by employing a child selector instead:
ol.alpha > li  { list-style: lower-alpha }
ul li   { list-style: disc }

   Another solution would be to specify 'list-style' information only on
   the list type elements:
ol.alpha  { list-style: lower-alpha }
ul        { list-style: disc }

   Inheritance will transfer the 'list-style' values from OL and UL
   elements to LI elements. This is the recommended way to specify list
   style information.

   Example(s):

   A URI value may be combined with any other value, as in:
ul { list-style: url("http://png.com/ellipse.png") disc }

   In the example above, the 'disc' will be used when the image is
   unavailable.

   A value of 'none' within the 'list-style' property sets whichever of
   'list-style-type' and 'list-style-image' are not otherwise specified to
   'none'. However, if both are otherwise specified, the declaration is in
   error (and thus ignored).

   Example(s):

   For example, a value of 'none' for the 'list-style' property sets both
   'list-style-type' and 'list-style-image' to 'none':
ul { list-style: none }

   The result is that no list-item marker is displayed.

                                 13 Paged media

   Contents
     * 13.1 Introduction to paged media
     * 13.2 Page boxes: the @page rule
          + 13.2.1 Page margins
          + 13.2.2 Page selectors: selecting left, right, and first pages
          + 13.2.3 Content outside the page box
     * 13.3 Page breaks
          + 13.3.1 Page break properties: 'page-break-before',
            'page-break-after', 'page-break-inside'
          + 13.3.2 Breaks inside elements: 'orphans', 'widows'
          + 13.3.3 Allowed page breaks
          + 13.3.4 Forced page breaks
          + 13.3.5 "Best" page breaks
     * 13.4 Cascading in the page context

13.1 Introduction to paged media

   Paged media (e.g., paper, transparencies, pages that are displayed on
   computer screens, etc.) differ from continuous media in that the
   content of the document is split into one or more discrete pages. To
   handle pages, CSS 2.1 describes how page margins are set on page boxes,
   and how page breaks are declared.

   The user agent is responsible for transferring the page boxes of a
   document onto the real sheets where the document will ultimately be
   rendered (paper, transparency, screen, etc.). There is often a 1-to-1
   relationship between a page box and a sheet, but this is not always the
   case. Transfer possibilities include:
     * Transferring one page box to one sheet (e.g., single-sided
       printing).
     * Transferring two page boxes to both sides of the same sheet (e.g.,
       double-sided printing).
     * Transferring N (small) page boxes to one sheet (called "n-up").
     * Transferring one (large) page box to N x M sheets (called
       "tiling").
     * Creating signatures. A signature is a group of pages printed on a
       sheet, which, when folded and trimmed like a book, appear in their
       proper sequence.
     * Printing one document to several output trays.
     * Outputting to a file.

13.2 Page boxes: the @page rule

   The page box is a rectangular region that contains two areas:
     * The page area. The page area includes the boxes laid out on that
       page. The edges of the first page area establish the rectangle that
       is the initial containing block of the document. The canvas
       background is painted within and covers the page area.
     * The margin area, which surrounds the page area. The page margin
       area is transparent.

   The size of a page box cannot be specified in CSS 2.1.

   Authors can specify the margins of a page box inside an @page rule. An
   @page rule consists of the keyword "@page", followed by an optional
   page selector, followed by a block containing declarations and
   at-rules. Comments and white space are allowed, but optional, between
   the @page token and the page selector and between the page selector and
   the block. The declarations in an @page rule are said to be in the page
   context.

   Note: CSS level 2 has no at-rules that may appear inside @page, but
   such at-rules are expected to be defined in level 3.

   The page selector specifies for which pages the declarations apply. In
   CSS 2.1, page selectors may designate the first page, all left pages,
   or all right pages

   The rules for handling malformed declarations, malformed statements,
   and invalid at-rules inside @page are as defined in section 4.2, with
   the following addition: when the UA expects the start of a declaration
   or at-rule (i.e., an IDENT token or an ATKEYWORD token) but finds an
   unexpected token instead, that token is considered to be the first
   token of a malformed declaration. I.e., the rule for malformed
   declarations, rather than malformed statements is used to determine
   which tokens to ignore in that case.

  13.2.1 Page margins

   In CSS 2.1, only the margin properties ('margin-top', 'margin-right',
   'margin-bottom', 'margin-left', and 'margin') apply within the page
   context. The following diagram shows the relationships between the
   sheet, page box, and page margins:

   Illustration of sheet, page box, margin, and page area.    [D]

   Example(s):

   Here is a simple example which sets all page margins on all pages:
@page {
  margin: 3cm;
}

   The page context has no notion of fonts, so 'em' and 'ex' units are not
   allowed. Percentage values on the margin properties are relative to the
   dimensions of the page box; for left and right margins, they refer to
   the width of the page box while for top and bottom margins, they refer
   to the height of the page box. All other units associated with the
   respective CSS 2.1 properties are allowed.

   Due to negative margin values (either on the page box or on elements)
   or absolute positioning content may end up outside the page box, but
   this content may be "cut" — by the user agent, the printer, or
   ultimately, the paper cutter.

  13.2.2 Page selectors: selecting left, right, and first pages

   When printing double-sided documents, the page boxes on left and right
   pages may be different. This can be expressed through two CSS
   pseudo-classes that may be used in page selectors.

   All pages are automatically classified by user agents into either the
   :left or :right pseudo-class. Whether the first page of a document is
   :left or :right depends on the major writing direction of the root
   element. For example, the first page of a document with a left-to-right
   major writing direction would be a :right page, and the first page of a
   document with a right-to-left major writing direction would be a :left
   page. To explicitly force a document to begin printing on a left or
   right page, authors can insert a page break before the first generated
   box.

   Example(s):

@page :left {
  margin-left: 4cm;
  margin-right: 3cm;
}

@page :right {
  margin-left: 3cm;
  margin-right: 4cm;
}

   If different declarations have been given for left and right pages, the
   user agent must honor these declarations even if the user agent does
   not transfer the page boxes to left and right sheets (e.g., a printer
   that only prints single-sided).

   Authors may also specify style for the first page of a document with
   the :first pseudo-class:

   Example(s):

@page { margin: 2cm } /* All margins set to 2cm */

@page :first {
  margin-top: 10cm    /* Top margin on first page 10cm */
}

   Properties specified in a :left or :right @page rule override those
   specified in an @page rule that has no pseudo-class specified.
   Properties specified in a :first @page rule override those specified in
   :left or :right @page rules.

   If a forced break occurs before the first generated box, it is
   undefined in CSS 2.1 whether ':first' applies to the blank page before
   the break or to the page after it.

   Margin declarations on left, right, and first pages may result in
   different page area widths. To simplify implementations, user agents
   may use a single page area width on left, right, and first pages. In
   this case, the page area width of the first page should be used.

  13.2.3 Content outside the page box

   When formatting content in the page model, some content may end up
   outside the current page box. For example, an element whose
   'white-space' property has the value 'pre' may generate a box that is
   wider than the page box. As another example, when boxes are positioned
   absolutely or relatively, they may end up in "inconvenient" locations.
   For example, images may be placed on the edge of the page box or
   100,000 meters below the page box.

   The exact formatting of such elements lies outside the scope of this
   specification. However, we recommend that authors and user agents
   observe the following general principles concerning content outside the
   page box:
     * Content should be allowed slightly beyond the page box to allow
       pages to "bleed".
     * User agents should avoid generating a large number of empty page
       boxes to honor the positioning of elements (e.g., you do not want
       to print 100 blank pages).
     * Authors should not position elements in inconvenient locations just
       to avoid rendering them.
     * User agents may handle boxes positioned outside the page box in
       several ways, including discarding them or creating page boxes for
       them at the end of the document.

13.3 Page breaks

   This section describes page breaks in CSS 2.1. Five properties indicate
   where the user agent may or should break pages, and on what page (left
   or right) the subsequent content should resume. Each page break ends
   layout in the current page box and causes remaining pieces of the
   document tree to be laid out in a new page box.

  13.3.1 Page break properties: 'page-break-before', 'page-break-after',
  'page-break-inside'

   'page-break-before'

          Value:            auto | always | avoid | left | right | inherit
          Initial:          auto
          Applies to:       block-level elements (but see text)
          Inherited:        no
          Percentages:      N/A
          Media:            visual, paged
          Computed value:   as specified

   'page-break-after'

          Value:            auto | always | avoid | left | right | inherit
          Initial:          auto
          Applies to:       block-level elements (but see text)
          Inherited:        no
          Percentages:      N/A
          Media:            visual, paged
          Computed value:   as specified

   'page-break-inside'

          Value:            avoid | auto | inherit
          Initial:          auto
          Applies to:       block-level elements (but see text)
          Inherited:        no
          Percentages:      N/A
          Media:            visual, paged
          Computed value:   as specified

   Values for these properties have the following meanings:

   auto
          Neither force nor forbid a page break before (after, inside) the
          generated box.

   always
          Always force a page break before (after) the generated box.

   avoid
          Avoid a page break before (after, inside) the generated box.

   left
          Force one or two page breaks before (after) the generated box so
          that the next page is formatted as a left page.

   right
          Force one or two page breaks before (after) the generated box so
          that the next page is formatted as a right page.

   A conforming user agent may interpret the values 'left' and 'right' as
   'always'.

   A potential page break location is typically under the influence of the
   parent element's 'page-break-inside' property, the 'page-break-after'
   property of the preceding element, and the 'page-break-before' property
   of the following element. When these properties have values other than
   'auto', the values 'always', 'left', and 'right' take precedence over
   'avoid'.

   User Agents must apply these properties to block-level elements in the
   normal flow of the root element. User agents may also apply these
   properties to other elements, e.g., 'table-row' elements.

   When a page break splits a box, the box's margins, borders, and padding
   have no visual effect where the split occurs.

  13.3.2 Breaks inside elements: 'orphans', 'widows'

   'orphans'

          Value:            <integer> | inherit
          Initial:          2
          Applies to:       block container elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual, paged
          Computed value:   as specified

   'widows'

          Value:            <integer> | inherit
          Initial:          2
          Applies to:       block container elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual, paged
          Computed value:   as specified

   The 'orphans' property specifies the minimum number of lines in a block
   container that must be left at the bottom of a page. The 'widows'
   property specifies the minimum number of lines in a block container
   that must be left at the top of a page. Examples of how they are used
   to control page breaks are given below.

   Only positive values are allowed.

   For information about paragraph formatting, please consult the section
   on line boxes.

  13.3.3 Allowed page breaks

   In the normal flow, page breaks can occur at the following places:
    1. In the vertical margin between block-level boxes. When an unforced
       page break occurs here, the used values of the relevant
       'margin-top' and 'margin-bottom' properties are set to '0'. When a
       forced page break occurs here, the used value of the relevant
       'margin-bottom' property is set to '0'; the relevant 'margin-top'
       used value may either be set to '0' or retained.
    2. Between line boxes inside a block container box.
    3. Between the content edge of a block container box and the outer
       edges of its child content (margin edges of block-level children or
       line box edges for inline-level children) if there is a (non-zero)
       gap between them.

   Note: It is expected that CSS3 will specify that the relevant
   'margin-top' applies (i.e., is not set to '0') after a forced page
   break.

   These breaks are subject to the following rules:
     * Rule A: Breaking at (1) is allowed only if the 'page-break-after'
       and 'page-break-before' properties of all the elements generating
       boxes that meet at this margin allow it, which is when at least one
       of them has the value 'always', 'left', or 'right', or when all of
       them are 'auto'.
     * Rule B: However, if all of them are 'auto' and a common ancestor of
       all the elements has a 'page-break-inside' value of 'avoid', then
       breaking here is not allowed.
     * Rule C: Breaking at (2) is allowed only if the number of line boxes
       between the break and the start of the enclosing block box is the
       value of 'orphans' or more, and the number of line boxes between
       the break and the end of the box is the value of 'widows' or more.
     * Rule D: In addition, breaking at (2) or (3) is allowed only if the
       'page-break-inside' property of the element and all its ancestors
       is 'auto'.

   If the above does not provide enough break points to keep content from
   overflowing the page boxes, then rules A, B and D are dropped in order
   to find additional breakpoints.

   If that still does not lead to sufficient break points, rule C is
   dropped as well, to find still more break points.

  13.3.4 Forced page breaks

   A page break must occur at (1) if, among the 'page-break-after' and
   'page-break-before' properties of all the elements generating boxes
   that meet at this margin, there is at least one with the value
   'always', 'left', or 'right'.

  13.3.5 "Best" page breaks

   CSS 2.1 does not define which of a set of allowed page breaks must be
   used; CSS 2.1 does not forbid a user agent from breaking at every
   possible break point, or not to break at all. But CSS 2.1 does
   recommend that user agents observe the following heuristics (while
   recognizing that they are sometimes contradictory):
     * Break as few times as possible.
     * Make all pages that do not end with a forced break appear to have
       about the same height.
     * Avoid breaking inside a replaced element.

   Example(s):

   Suppose, for example, that the style sheet contains 'orphans: 4',
   'widows: 2', and there are 20 lines (line boxes) available at the
   bottom of the current page:
     * If a paragraph at the end of the current page contains 20 lines or
       fewer, it should be placed on the current page.
     * If the paragraph contains 21 or 22 lines, the second part of the
       paragraph must not violate the 'widows' constraint, and so the
       second part must contain exactly two lines
     * If the paragraph contains 23 lines or more, the first part should
       contain 20 lines and the second part the remaining lines.

   Now suppose that 'orphans' is '10', 'widows' is '20', and there are 8
   lines available at the bottom of the current page:
     * If a paragraph at the end of the current page contains 8 lines or
       fewer, it should be placed on the current page.
     * If the paragraph contains 9 lines or more, it cannot be split (that
       would violate the orphan constraint), so it should move as a block
       to the next page.

13.4 Cascading in the page context

   Declarations in the page context obey the cascade just like normal CSS
   declarations.

   Example(s):

   Consider the following example:
@page {
  margin-left: 3cm;
}

@page :left {
  margin-left: 4cm;
}

   Due to the higher specificity of the pseudo-class selector, the left
   margin on left pages will be '4cm' and all other pages (i.e., the right
   pages) will have a left margin of '3cm'.

                           14 Colors and Backgrounds

   Contents
     * 14.1 Foreground color: the 'color' property
     * 14.2 The background
          + 14.2.1 Background properties: 'background-color',
            'background-image', 'background-repeat',
            'background-attachment', 'background-position', and
            'background'

   CSS properties allow authors to specify the foreground color and
   background of an element. Backgrounds may be colors or images.
   Background properties allow authors to position a background image,
   repeat it, and declare whether it should be fixed with respect to the
   viewport or scrolled along with the document.

   See the section on color units for the syntax of valid color values.

14.1 Foreground color: the 'color' property

   'color'

          Value:            <color> | inherit
          Initial:          depends on user agent
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property describes the foreground color of an element's text
   content. There are different ways to specify red:

   Example(s):
em { color: red }              /* predefined color name */
em { color: rgb(255,0,0) }     /* RGB range 0-255   */

14.2 The background

   Authors may specify the background of an element (i.e., its rendering
   surface) as either a color or an image. In terms of the box model,
   "background" refers to the background of the content, padding and
   border areas. Border colors and styles are set with the border
   properties. Margins are always transparent.

   Background properties are not inherited, but the parent box's
   background will shine through by default because of the initial
   'transparent' value on 'background-color'.

   The background of the root element becomes the background of the canvas
   and covers the entire canvas, anchored (for 'background-position') at
   the same point as it would be if it was painted only for the root
   element itself. The root element does not paint this background again.

   For HTML documents, however, we recommend that authors specify the
   background for the BODY element rather than the HTML element. For
   documents whose root element is an HTML "HTML" element or an XHTML
   "html" element that has computed values of 'transparent' for
   'background-color' and 'none' for 'background-image', user agents must
   instead use the computed value of the background properties from that
   element's first HTML "BODY" element or XHTML "body" element child when
   painting backgrounds for the canvas, and must not paint a background
   for that child element. Such backgrounds must also be anchored at the
   same point as they would be if they were painted only for the root
   element.

   According to these rules, the canvas underlying the following HTML
   document will have a "marble" background:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
    <TITLE>Setting the canvas background</TITLE>
    <STYLE type="text/css">
       BODY { background: url("http://example.com/marble.png") }
    </STYLE>
    <P>My background is marble.

   Note that the rule for the BODY element will work even though the BODY
   tag has been omitted in the HTML source since the HTML parser will
   infer the missing tag.

   Backgrounds of elements that form a stacking context (see the 'z-index'
   property) are painted at the bottom of the element's stacking context,
   below anything in that stacking context.

  14.2.1 Background properties: 'background-color', 'background-image',
  'background-repeat', 'background-attachment', 'background-position', and
  'background'

   'background-color'

          Value:            <color> | transparent | inherit
          Initial:          transparent
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property sets the background color of an element, either a <color>
   value or the keyword 'transparent', to make the underlying colors shine
   through.

   Example(s):
h1 { background-color: #F00 }

   'background-image'

          Value:            <uri> | none | inherit
          Initial:          none
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   absolute URI or none

   This property sets the background image of an element. When setting a
   background image, authors should also specify a background color that
   will be used when the image is unavailable. When the image is
   available, it is rendered on top of the background color. (Thus, the
   color is visible in the transparent parts of the image).

   Values for this property are either <uri>, to specify the image, or
   'none', when no image is used.

   Example(s):
body { background-image: url("marble.png") }
p { background-image: none }

   Intrinsic dimensions expressed as percentages must be resolved relative
   to the dimensions of the rectangle that establishes the coordinate
   system for the 'background-position' property.

   If the image has one of either an intrinsic width or an intrinsic
   height and an intrinsic aspect ratio, then the missing dimension is
   calculated from the given dimension and the ratio.

   If the image has one of either an intrinsic width or an intrinsic
   height and no intrinsic aspect ratio, then the missing dimension is
   assumed to be the size of the rectangle that establishes the coordinate
   system for the 'background-position' property.

   If the image has no intrinsic dimensions and has an intrinsic ratio the
   dimensions must be assumed to be the largest dimensions at that ratio
   such that neither dimension exceeds the dimensions of the rectangle
   that establishes the coordinate system for the 'background-position'
   property.

   If the image has no intrinsic ratio either, then the dimensions must be
   assumed to be the rectangle that establishes the coordinate system for
   the 'background-position' property.

   'background-repeat'

          Value:            repeat | repeat-x | repeat-y | no-repeat | inherit
          Initial:          repeat
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   If a background image is specified, this property specifies whether the
   image is repeated (tiled), and how. All tiling covers the content,
   padding and border areas of a box.

   The tiling and positioning of the background-image on inline elements
   is undefined in this specification. A future level of CSS may define
   the tiling and positioning of the background-image on inline elements.

   Values have the following meanings:

   repeat
          The image is repeated both horizontally and vertically.

   repeat-x
          The image is repeated horizontally only.

   repeat-y
          The image is repeated vertically only.

   no-repeat
          The image is not repeated: only one copy of the image is drawn.

   Example(s):
body {
  background: white url("pendant.png");
  background-repeat: repeat-y;
  background-position: center;
}

   A centered background image, with copies repeated up and down the
   padding and content areas.    [D]

   One copy of the background image is centered, and other copies are put
   above and below it to make a vertical band behind the element.

   'background-attachment'

          Value:            scroll | fixed | inherit
          Initial:          scroll
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   If a background image is specified, this property specifies whether it
   is fixed with regard to the viewport ('fixed') or scrolls along with
   the containing block ('scroll').

   Note that there is only one viewport per view. If an element has a
   scrolling mechanism (see 'overflow'), a 'fixed' background does not
   move with the element, and a 'scroll' background does not move with the
   scrolling mechanism.

   Even if the image is fixed, it is still only visible when it is in the
   content, padding or border area of the element. Thus, unless the image
   is tiled ('background-repeat: repeat'), it may be invisible.

   In paged media, where there is no viewport, a 'fixed' background is
   fixed with respect to the page box and is therefore replicated on every
   page.

   Example(s):

   This example creates an infinite vertical band that remains "glued" to
   the viewport when the element is scrolled.
body {
  background: red url("pendant.png");
  background-repeat: repeat-y;
  background-attachment: fixed;
}

   User agents that do not support 'fixed' backgrounds (for example due to
   limitations of the hardware platform) should ignore declarations with
   the keyword 'fixed'. For example:
body {
  background: white url(paper.png) scroll; /* for all UAs */
  background: white url(ledger.png) fixed; /* for UAs that do fixed backgrounds
*/
}

   See the section on conformance for details.

   'background-position'

   Value:   [ [ <percentage> | <length> | left | center | right ] [
   <percentage> | <length> | top | center | bottom ]? ] | [ [ left |
   center | right ] || [ top | center | bottom ] ] | inherit
   Initial:   0% 0%
   Applies to:   all elements
   Inherited:   no
   Percentages:   refer to the size of the box itself
   Media:   visual
   Computed value:   for <length> the absolute value, otherwise a
   percentage

   If a background image has been specified, this property specifies its
   initial position. If only one value is specified, the second value is
   assumed to be 'center'. If at least one value is not a keyword, then
   the first value represents the horizontal position and the second
   represents the vertical position. Negative <percentage> and <length>
   values are allowed.

   <percentage>
          A percentage X aligns the point X% across (for horizontal) or
          down (for vertical) the image with the point X% across (for
          horizontal) or down (for vertical) the element's padding box.
          For example, with a value pair of '0% 0%',the upper left corner
          of the image is aligned with the upper left corner of the
          padding box. A value pair of '100% 100%' places the lower right
          corner of the image in the lower right corner of the padding
          box. With a value pair of '14% 84%', the point 14% across and
          84% down the image is to be placed at the point 14% across and
          84% down the padding box.

   <length>
          A length L aligns the top left corner of the image a distance L
          to the right of (for horizontal) or below (for vertical) the top
          left corner of the element's padding box. For example, with a
          value pair of '2cm 1cm', the upper left corner of the image is
          placed 2cm to the right and 1cm below the upper left corner of
          the padding box.

   top
          Equivalent to '0%' for the vertical position.

   right
          Equivalent to '100%' for the horizontal position.

   bottom
          Equivalent to '100%' for the vertical position.

   left
          Equivalent to '0%' for the horizontal position.

   center
          Equivalent to '50%' for the horizontal position if it is not
          otherwise given, or '50%' for the vertical position if it is.

   However, the position is undefined in CSS 2.1 if the image has an
   intrinsic ratio, but no intrinsic size.

   Example(s):
body { background: url("banner.jpeg") right top }    /* 100%   0% */
body { background: url("banner.jpeg") top center }   /*  50%   0% */
body { background: url("banner.jpeg") center }       /*  50%  50% */
body { background: url("banner.jpeg") bottom }       /*  50% 100% */

   The tiling and positioning of the background-image on inline elements
   is undefined in this specification. A future level of CSS may define
   the tiling and positioning of the background-image on inline elements.

   If the background image is fixed within the viewport (see the
   'background-attachment' property), the image is placed relative to the
   viewport instead of the element's padding box. For example,

   Example(s):
body {
  background-image: url("logo.png");
  background-attachment: fixed;
  background-position: 100% 100%;
  background-repeat: no-repeat;
}

   In the example above, the (single) image is placed in the lower-right
   corner of the viewport.

   'background'

         Value:            [<'background-color'> || <'background-image'> ||
                           <'background-repeat'> || <'background-attachment'> ||
                           <'background-position'>] | inherit
         Initial:          see individual properties
         Applies to:       all elements
         Inherited:        no
         Percentages:      allowed on 'background-position'
         Media:            visual
         Computed value:   see individual properties

   The 'background' property is a shorthand property for setting the
   individual background properties (i.e., 'background-color',
   'background-image', 'background-repeat', 'background-attachment' and
   'background-position') at the same place in the style sheet.

   Given a valid declaration, the 'background' property first sets all the
   individual background properties to their initial values, then assigns
   explicit values given in the declaration.

   Example(s):

   In the first rule of the following example, only a value for
   'background-color' has been given and the other individual properties
   are set to their initial value. In the second rule, all individual
   properties have been specified.
BODY { background: red }
P { background: url("chess.png") gray 50% repeat fixed }

                                    15 Fonts

   Contents
     * 15.1 Introduction
     * 15.2 Font matching algorithm
     * 15.3 Font family: the 'font-family' property
          + 15.3.1 Generic font families
               o 15.3.1.1 serif
               o 15.3.1.2 sans-serif
               o 15.3.1.3 cursive
               o 15.3.1.4 fantasy
               o 15.3.1.5 monospace
     * 15.4 Font styling: the 'font-style' property
     * 15.5 Small-caps: the 'font-variant' property
     * 15.6 Font boldness: the 'font-weight' property
     * 15.7 Font size: the 'font-size' property
     * 15.8 Shorthand font property: the 'font' property

15.1 Introduction

   Setting font properties will be among the most common uses of style
   sheets. Unfortunately, there exists no well-defined and universally
   accepted taxonomy for classifying fonts, and terms that apply to one
   font family may not be appropriate for others. E.g., 'italic' is
   commonly used to label slanted text, but slanted text may also be
   labeled as being Oblique, Slanted, Incline, Cursive or Kursiv.
   Therefore it is not a simple problem to map typical font selection
   properties to a specific font.

15.2 Font matching algorithm

   Because there is no accepted, universal taxonomy of font properties,
   matching of properties to font faces must be done carefully. The
   properties are matched in a well-defined order to insure that the
   results of this matching process are as consistent as possible across
   UAs (assuming that the same library of font faces is presented to each
   of them).
    1. The User Agent makes (or accesses) a database of relevant CSS 2.1
       properties of all the fonts of which the UA is aware. If there are
       two fonts with exactly the same properties, the user agent selects
       one of them.
    2. At a given element and for each character in that element, the UA
       assembles the font properties applicable to that element. Using the
       complete set of properties, the UA uses the 'font-family' property
       to choose a tentative font family. The remaining properties are
       tested against the family according to the matching criteria
       described with each property. If there are matches for all the
       remaining properties, then that is the matching font face for the
       given element or character.
    3. If there is no matching font face within the 'font-family' being
       processed by step 2, and if there is a next alternative
       'font-family' in the font set, then repeat step 2 with the next
       alternative 'font-family'.
    4. If there is a matching font face, but it does not contain a glyph
       for the current character, and if there is a next alternative
       'font-family' in the font sets, then repeat step 2 with the next
       alternative 'font-family'.
    5. If there is no font within the family selected in 2, then use a
       UA-dependent default 'font-family' and repeat step 2, using the
       best match that can be obtained within the default font. If a
       particular character cannot be displayed using this font, then the
       UA may use other means to determine a suitable font for that
       character. The UA should map each character for which it has no
       suitable font to a visible symbol chosen by the UA, preferably a
       "missing character" glyph from one of the font faces available to
       the UA.

   (The above algorithm can be optimized to avoid having to revisit the
   CSS 2.1 properties for each character.)

   The per-property matching rules from (2) above are as follows:
    1. 'font-style' is tried first. 'Italic' will be satisfied if there is
       either a face in the UA's font database labeled with the CSS
       keyword 'italic' (preferred) or 'oblique'. Otherwise the values
       must be matched exactly or font-style will fail.
    2. 'font-variant' is tried next. 'Small-caps' matches (1) a font
       labeled as 'small-caps', (2) a font in which the small caps are
       synthesized, or (3) a font where all lowercase letters are replaced
       by upper case letters. A small-caps font may be synthesized by
       electronically scaling uppercase letters from a normal font.
       'normal' matches a font's normal (non-small-caps) variant. A font
       cannot fail to have a normal variant. A font that is only available
       as small-caps shall be selectable as either a 'normal' face or a
       'small-caps' face.
    3. 'font-weight' is matched next, it will never fail. (See
       'font-weight' below.)
    4. 'font-size' must be matched within a UA-dependent margin of
       tolerance. (Typically, sizes for scalable fonts are rounded to the
       nearest whole pixel, while the tolerance for bitmapped fonts could
       be as large as 20%.) Further computations, e.g., by 'em' values in
       other properties, are based on the computed value of 'font-size'.

15.3 Font family: the 'font-family' property

   'font-family'

       Value:            [[ <family-name> | <generic-family> ] [, <family-name>|
                         <generic-family>]* ] | inherit
       Initial:          depends on user agent
       Applies to:       all elements
       Inherited:        yes
       Percentages:      N/A
       Media:            visual
       Computed value:   as specified

   The property value is a prioritized list of font family names and/or
   generic family names. Unlike most other CSS properties, component
   values are separated by a comma to indicate that they are alternatives:
body { font-family: Gill, Helvetica, sans-serif }

   Although many fonts provide the "missing character" glyph, typically an
   open box, as its name implies this should not be considered a match for
   characters that cannot be found in the font. (It should, however, be
   considered a match for U+FFFD, the "missing character" character's code
   point).

   There are two types of font family names:

   <family-name>
          The name of a font family of choice. In the last example, "Gill"
          and "Helvetica" are font families.

   <generic-family>
          In the example above, the last value is a generic family name.
          The following generic families are defined:

          + 'serif' (e.g., Times)
          + 'sans-serif' (e.g., Helvetica)
          + 'cursive' (e.g., Zapf-Chancery)
          + 'fantasy' (e.g., Western)
          + 'monospace' (e.g., Courier)

          Style sheet designers are encouraged to offer a generic font
          family as a last alternative. Generic font family names are
          keywords and must NOT be quoted.

   Font family names must either be given quoted as strings, or unquoted
   as a sequence of one or more identifiers. This means most punctuation
   characters and digits at the start of each token must be escaped in
   unquoted font family names.

   For example, the following declarations are invalid:
font-family: Red/Black, sans-serif;
font-family: "Lucida" Grande, sans-serif;
font-family: Ahem!, sans-serif;
font-family: test@foo, sans-serif;
font-family: #POUND, sans-serif;
font-family: Hawaii 5-0, sans-serif;

   If a sequence of identifiers is given as a font family name, the
   computed value is the name converted to a string by joining all the
   identifiers in the sequence by single spaces.

   To avoid mistakes in escaping, it is recommended to quote font family
   names that contain white space, digits, or punctuation characters other
   than hyphens:
body { font-family: "New Century Schoolbook", serif }

<BODY STYLE="font-family: '21st Century', fantasy">

   Font family names that happen to be the same as a keyword value
   ('inherit', 'serif', 'sans-serif', 'monospace', 'fantasy', and
   'cursive') must be quoted to prevent confusion with the keywords with
   the same names. The keywords 'initial' and 'default' are reserved for
   future use and must also be quoted when used as font names. UAs must
   not consider these keywords as matching the '<family-name>' type.

  15.3.1 Generic font families

   Generic font families are a fallback mechanism, a means of preserving
   some of the style sheet author's intent in the worst case when none of
   the specified fonts can be selected. For optimum typographic control,
   particular named fonts should be used in style sheets.

   All five generic font families are defined to exist in all CSS
   implementations (they need not necessarily map to five distinct actual
   fonts). User agents should provide reasonable default choices for the
   generic font families, which express the characteristics of each family
   as well as possible within the limits allowed by the underlying
   technology.

   User agents are encouraged to allow users to select alternative choices
   for the generic fonts.

    15.3.1.1 serif

   Glyphs of serif fonts, as the term is used in CSS, tend to have
   finishing strokes, flared or tapering ends, or have actual serifed
   endings (including slab serifs). Serif fonts are typically
   proportionately-spaced. They often display a greater variation between
   thick and thin strokes than fonts from the 'sans-serif' generic font
   family. CSS uses the term 'serif' to apply to a font for any script,
   although other names may be more familiar for particular scripts, such
   as Mincho (Japanese), Sung or Song (Chinese), Totum or Kodig (Korean).
   Any font that is so described may be used to represent the generic
   'serif' family.

   Examples of fonts that fit this description include:

   Latin fonts    Times New Roman, Bodoni, Garamond, Minion Web, ITC Stone
                  Serif, MS Georgia, Bitstream Cyberbit
   Greek fonts    Bitstream Cyberbit
   Cyrillic fonts Adobe Minion Cyrillic, Excelsior Cyrillic Upright,
                  Monotype Albion 70, Bitstream Cyberbit, ER Bukinist
   Hebrew fonts   New Peninim, Raanana, Bitstream Cyberbit
   Japanese fonts Ryumin Light-KL, Kyokasho ICA, Futo Min A101
   Arabic fonts   Bitstream Cyberbit
   Cherokee fonts Lo Cicero Cherokee

    15.3.1.2 sans-serif

   Glyphs in sans-serif fonts, as the term is used in CSS, tend to have
   stroke endings that are plain -- with little or no flaring, cross
   stroke, or other ornamentation. Sans-serif fonts are typically
   proportionately-spaced. They often have little variation between thick
   and thin strokes, compared to fonts from the 'serif' family. CSS uses
   the term 'sans-serif' to apply to a font for any script, although other
   names may be more familiar for particular scripts, such as Gothic
   (Japanese), Kai (Chinese), or Pathang (Korean). Any font that is so
   described may be used to represent the generic 'sans-serif' family.

   Examples of fonts that fit this description include:

   Latin fonts MS Trebuchet, ITC Avant Garde Gothic, MS Arial, MS Verdana,
   Univers, Futura, ITC Stone Sans, Gill Sans, Akzidenz Grotesk, Helvetica
   Greek fonts Attika, Typiko New Era, MS Tahoma, Monotype Gill Sans 571,
   Helvetica Greek
   Cyrillic fonts Helvetica Cyrillic, ER Univers, Lucida Sans Unicode,
   Bastion
   Hebrew fonts Arial Hebrew, MS Tahoma
   Japanese fonts Shin Go, Heisei Kaku Gothic W5
   Arabic fonts MS Tahoma

    15.3.1.3 cursive

   Glyphs in cursive fonts, as the term is used in CSS, generally have
   either joining strokes or other cursive characteristics beyond those of
   italic typefaces. The glyphs are partially or completely connected, and
   the result looks more like handwritten pen or brush writing than
   printed letterwork. Fonts for some scripts, such as Arabic, are almost
   always cursive. CSS uses the term 'cursive' to apply to a font for any
   script, although other names such as Chancery, Brush, Swing and Script
   are also used in font names.

   Examples of fonts that fit this description include:

   Latin fonts    Caflisch Script, Adobe Poetica, Sanvito, Ex Ponto, Snell
                  Roundhand, Zapf-Chancery
   Cyrillic fonts ER Architekt
   Hebrew fonts   Corsiva
   Arabic fonts   DecoType Naskh, Monotype Urdu 507

    15.3.1.4 fantasy

   Fantasy fonts, as used in CSS, are primarily decorative while still
   containing representations of characters (as opposed to Pi or Picture
   fonts, which do not represent characters). Examples include:

   Latin fonts Alpha Geometrique, Critter, Cottonwood, FB Reactor, Studz

    15.3.1.5 monospace

   The sole criterion of a monospace font is that all glyphs have the same
   fixed width. (This can make some scripts, such as Arabic, look most
   peculiar.) The effect is similar to a manual typewriter, and is often
   used to set samples of computer code.

   Examples of fonts which fit this description include:

   Latin fonts    Courier, MS Courier New, Prestige, Everson Mono
   Greek Fonts    MS Courier New, Everson Mono
   Cyrillic fonts ER Kurier, Everson Mono
   Japanese fonts Osaka Monospaced
   Cherokee fonts Everson Mono

15.4 Font styling: the 'font-style' property

   'font-style'

          Value:            normal | italic | oblique | inherit
          Initial:          normal
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   The 'font-style' property selects between normal (sometimes referred to
   as "roman" or "upright"), italic and oblique faces within a font
   family.

   A value of 'normal' selects a font that is classified as 'normal' in
   the UA's font database, while 'oblique' selects a font that is labeled
   'oblique'. A value of 'italic' selects a font that is labeled 'italic',
   or, if that is not available, one labeled 'oblique'.

   The font that is labeled 'oblique' in the UA's font database may
   actually have been generated by electronically slanting a normal font.

   Fonts with Oblique, Slanted or Incline in their names will typically be
   labeled 'oblique' in the UA's font database. Fonts with Italic, Cursive
   or Kursiv in their names will typically be labeled 'italic'.
h1, h2, h3 { font-style: italic }
h1 em { font-style: normal }

   In the example above, emphasized text within 'H1' will appear in a
   normal face.

15.5 Small-caps: the 'font-variant' property

   'font-variant'

          Value:            normal | small-caps | inherit
          Initial:          normal
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   Another type of variation within a font family is the small-caps. In a
   small-caps font the lower case letters look similar to the uppercase
   ones, but in a smaller size and with slightly different proportions.
   The 'font-variant' property selects that font.

   A value of 'normal' selects a font that is not a small-caps font,
   'small-caps' selects a small-caps font. It is acceptable (but not
   required) in CSS 2.1 if the small-caps font is a created by taking a
   normal font and replacing the lower case letters by scaled uppercase
   characters. As a last resort, uppercase letters will be used as
   replacement for a small-caps font.

   The following example results in an 'H3' element in small-caps, with
   any emphasized words in oblique, and any emphasized words within an
   'H3' oblique small-caps:
h3 { font-variant: small-caps }
em { font-style: oblique }

   There may be other variants in the font family as well, such as fonts
   with old-style numerals, small-caps numerals, condensed or expanded
   letters, etc. CSS 2.1 has no properties that select those.

   Note: insofar as this property causes text to be transformed to
   uppercase, the same considerations as for 'text-transform' apply.

15.6 Font boldness: the 'font-weight' property

   'font-weight'

Value:            normal | bold | bolder | lighter | 100 | 200 | 300 | 400 | 500
                  | 600 | 700 | 800 | 900 | inherit
Initial:          normal
Applies to:       all elements
Inherited:        yes
Percentages:      N/A
Media:            visual
Computed value:   see text

   The 'font-weight' property selects the weight of the font. The values
   '100' to '900' form an ordered sequence, where each number indicates a
   weight that is at least as dark as its predecessor. The keyword
   'normal' is synonymous with '400', and 'bold' is synonymous with '700'.
   Keywords other than 'normal' and 'bold' have been shown to be often
   confused with font names and a numerical scale was therefore chosen for
   the 9-value list.
p { font-weight: normal }   /* 400 */
h1 { font-weight: 700 }     /* bold */

   The 'bolder' and 'lighter' values select font weights that are relative
   to the weight inherited from the parent:
strong { font-weight: bolder }

   Fonts (the font data) typically have one or more properties whose
   values are names that are descriptive of the "weight" of a font. There
   is no accepted, universal meaning to these weight names. Their primary
   role is to distinguish faces of differing darkness within a single font
   family. Usage across font families is quite variant; for example, a
   font that one might think of as being bold might be described as being
   Regular, Roman, Book, Medium, Semi- or DemiBold, Bold, or Black,
   depending on how black the "normal" face of the font is within the
   design. Because there is no standard usage of names, the weight
   property values in CSS 2.1 are given on a numerical scale in which the
   value '400' (or 'normal') corresponds to the "normal" text face for
   that family. The weight name associated with that face will typically
   be Book, Regular, Roman, Normal or sometimes Medium.

   The association of other weights within a family to the numerical
   weight values is intended only to preserve the ordering of darkness
   within that family. However, the following heuristics tell how the
   assignment is done in this case:
     * If the font family already uses a numerical scale with nine values
       (like e.g., OpenType does), the font weights should be mapped
       directly.
     * If there is both a face labeled Medium and one labeled Book,
       Regular, Roman or Normal, then the Medium is normally assigned to
       the '500'.
     * The font labeled "Bold" will often correspond to the weight value
       '700'.

   Once the font family's weights are mapped onto the CSS scale, missing
   weights are selected as follows:
     * If the desired weight is less than 400, weights below the desired
       weight are checked in descending order followed by weights above
       the desired weight in ascending order until a match is found.
     * If the desired weight is greater than 500, weights above desired
       weight are checked in ascending order followed by weights below the
       desired weight in descending order until a match is found.
     * If the desired weight is 400, 500 is checked first and then the
       rule for desired weights less than 400 is used.
     * If the desired weight is 500, 400 is checked first and then the
       rule for desired weights less than 400 is used.

   The following two examples show typical mappings.

   Assume four weights in the "Rattlesnake" family, from lightest to
   darkest: Regular, Medium, Bold, Heavy.

   CAPTION: First example of font-weight mapping

     Available faces     Assignments Filling the holes
   "Rattlesnake Regular" 400         100, 200, 300
   "Rattlesnake Medium"  500
   "Rattlesnake Bold"    700         600
   "Rattlesnake Heavy"   800         900

   Assume six weights in the "Ice Prawn" family: Book, Medium, Bold,
   Heavy, Black, ExtraBlack. Note that in this instance the user agent has
   decided not to assign a numeric value to "Ice Prawn ExtraBlack".

   CAPTION: Second example of font-weight mapping

      Available faces     Assignments Filling the holes
   "Ice Prawn Book"       400         100, 200, 300
   "Ice Prawn Medium"     500
   "Ice Prawn Bold"       700         600
   "Ice Prawn Heavy"      800
   "Ice Prawn Black"      900
   "Ice Prawn ExtraBlack" (none)

   Values of 'bolder' and 'lighter' indicate values relative to the weight
   of the parent element. Based on the inherited weight value, the weight
   used is calculated using the chart below. Child elements inherit the
   calculated weight, not a value of 'bolder' or 'lighter'.

   CAPTION: The meaning of 'bolder' and 'lighter'

   Inherited value bolder lighter
   100             400    100
   200             400    100
   300             400    100
   400             700    100
   500             700    100
   600             900    400
   700             900    400
   800             900    700
   900             900    700

   The table above is equivalent to selecting the next relative bolder or
   lighter face, given a font family containing normal and bold faces
   along with a thin and a heavy face. Authors who desire finer control
   over the exact weight values used for a given element should use
   numerical values instead of relative weights.

   There is no guarantee that there will be a darker face for each of the
   'font-weight' values; for example, some fonts may have only a normal
   and a bold face, while others may have eight face weights. There is no
   guarantee on how a UA will map font faces within a family to weight
   values. The only guarantee is that a face of a given value will be no
   less dark than the faces of lighter values.

15.7 Font size: the 'font-size' property

   'font-size'

 Value:            <absolute-size> | <relative-size> | <length> | <percentage> |
                   inherit
 Initial:          medium
 Applies to:       all elements
 Inherited:        yes
 Percentages:      refer to inherited font size
 Media:            visual
 Computed value:   absolute length

   The font size corresponds to the em square, a concept used in
   typography. Note that certain glyphs may bleed outside their em
   squares. Values have the following meanings:

   <absolute-size>
          An <absolute-size> keyword is an index to a table of font sizes
          computed and kept by the UA. Possible values are:

          [ xx-small | x-small | small | medium | large | x-large |
          xx-large ]

          The following table provides user agent guidelines for the
          absolute-size mapping to HTML heading and absolute font-sizes.
          The 'medium' value is the user's preferred font size and is used
          as the reference middle value.

 CSS absolute-size values xx-small x-small small medium large x-large
                                                                      xx-large
     HTML font sizes      1                2     3      4     5       6        7

          Implementors should build a table of scaling factors for
          absolute-size keywords relative to the 'medium' font size and
          the particular device and its characteristics (e.g., the
          resolution of the device).

          Different media may need different scaling factors. Also, the UA
          should take the quality and availability of fonts into account
          when computing the table. The table may be different from one
          font family to another.

          Note 1. To preserve readability, a UA applying these guidelines
          should nevertheless avoid creating font-size resulting in less
          than 9 pixels per EM unit on a computer display.

          Note 2. In CSS1, the suggested scaling factor between adjacent
          indexes was 1.5, which user experience proved to be too large.
          In CSS2, the suggested scaling factor for a computer screen
          between adjacent indexes was 1.2, which still created issues for
          the small sizes. Implementation experience has demonstrated that
          a fixed ratio between adjacent absolute-size keywords is
          problematic, and this specification does not recommend such a
          fixed ratio.

   <relative-size>
          A <relative-size> keyword is interpreted relative to the table
          of font sizes and the font size of the parent element. Possible
          values are: [ larger | smaller ]. For example, if the parent
          element has a font size of 'medium', a value of 'larger' will
          make the font size of the current element be 'large'. If the
          parent element's size is not close to a table entry, the UA is
          free to interpolate between table entries or round off to the
          closest one. The UA may have to extrapolate table values if the
          numerical value goes beyond the keywords.

   Length and percentage values should not take the font size table into
   account when calculating the font size of the element.

   Negative values are not allowed.

   On all other properties, 'em' and 'ex' length values refer to the
   computed font size of the current element. On the 'font-size' property,
   these length units refer to the computed font size of the parent
   element.

   Note that an application may reinterpret an explicit size, depending on
   the context. E.g., inside a VR scene a font may get a different size
   because of perspective distortion.

   Examples:
p { font-size: 16px; }
@media print {
        p { font-size: 12pt; }
}
blockquote { font-size: larger }
em { font-size: 150% }
em { font-size: 1.5em }

15.8 Shorthand font property: the 'font' property

   'font'

   Value:   [ [ <'font-style'> || <'font-variant'> || <'font-weight'> ]?
   <'font-size'> [ / <'line-height'> ]? <'font-family'> ] | caption | icon
   | menu | message-box | small-caption | status-bar | inherit
   Initial:   see individual properties
   Applies to:   all elements
   Inherited:   yes
   Percentages:   see individual properties
   Media:   visual
   Computed value:   see individual properties

   The 'font' property is, except as described below, a shorthand property
   for setting 'font-style', 'font-variant', 'font-weight', 'font-size',
   'line-height' and 'font-family' at the same place in the style sheet.
   The syntax of this property is based on a traditional typographical
   shorthand notation to set multiple properties related to fonts.

   All font-related properties are first reset to their initial values,
   including those listed in the preceding paragraph. Then, those
   properties that are given explicit values in the 'font' shorthand are
   set to those values. For a definition of allowed and initial values,
   see the previously defined properties.
p { font: 12px/14px sans-serif }
p { font: 80% sans-serif }
p { font: x-large/110% "New Century Schoolbook", serif }
p { font: bold italic large Palatino, serif }
p { font: normal small-caps 120%/120% fantasy }

   In the second rule, the font size percentage value ('80%') refers to
   the font size of the parent element. In the third rule, the line height
   percentage refers to the font size of the element itself.

   In the first three rules above, the 'font-style', 'font-variant' and
   'font-weight' are not explicitly mentioned, which means they are all
   three set to their initial value ('normal'). The fourth rule sets the
   'font-weight' to 'bold', the 'font-style' to 'italic' and implicitly
   sets 'font-variant' to 'normal'.

   The fifth rule sets the 'font-variant' ('small-caps'), the 'font-size'
   (120% of the parent's font), the 'line-height' (120% times the font
   size) and the 'font-family' ('fantasy'). It follows that the keyword
   'normal' applies to the two remaining properties: 'font-style' and
   'font-weight'.

   The following values refer to system fonts:

   caption
          The font used for captioned controls (e.g., buttons, drop-downs,
          etc.).

   icon
          The font used to label icons.

   menu
          The font used in menus (e.g., dropdown menus and menu lists).

   message-box
          The font used in dialog boxes.

   small-caption
          The font used for labeling small controls.

   status-bar
          The font used in window status bars.

   System fonts may only be set as a whole; that is, the font family,
   size, weight, style, etc. are all set at the same time. These values
   may then be altered individually if desired. If no font with the
   indicated characteristics exists on a given platform, the user agent
   should either intelligently substitute (e.g., a smaller version of the
   'caption' font might be used for the 'small-caption' font), or
   substitute a user agent default font. As for regular fonts, if, for a
   system font, any of the individual properties are not part of the
   operating system's available user preferences, those properties should
   be set to their initial values.

   That is why this property is "almost" a shorthand property: system
   fonts can only be specified with this property, not with 'font-family'
   itself, so 'font' allows authors to do more than the sum of its
   subproperties. However, the individual properties such as 'font-weight'
   are still given values taken from the system font, which can be
   independently varied.

   Example(s):
button { font: 300 italic 1.3em/1.7em "FB Armada", sans-serif }
button p { font: menu }
button p em { font-weight: bolder }

   If the font used for dropdown menus on a particular system happened to
   be, for example, 9-point Charcoal, with a weight of 600, then P
   elements that were descendants of BUTTON would be displayed as if this
   rule were in effect:
button p { font: 600 9px Charcoal }

   Because the 'font' shorthand property resets any property not
   explicitly given a value to its initial value, this has the same effect
   as this declaration:
button p {
  font-family: Charcoal;
  font-style: normal;
  font-variant: normal;
  font-weight: 600;
  font-size: 9px;
  line-height: normal;
}

                                    16 Text

   Contents
     * 16.1 Indentation: the 'text-indent' property
     * 16.2 Alignment: the 'text-align' property
     * 16.3 Decoration
          + 16.3.1 Underlining, overlining, striking, and blinking: the
            'text-decoration' property
     * 16.4 Letter and word spacing: the 'letter-spacing' and
       'word-spacing' properties
     * 16.5 Capitalization: the 'text-transform' property
     * 16.6 White space: the 'white-space' property
          + 16.6.1 The 'white-space' processing model
          + 16.6.2 Example of bidirectionality with white space collapsing
          + 16.6.3 Control and combining characters' details

   The properties defined in the following sections affect the visual
   presentation of characters, spaces, words, and paragraphs.

16.1 Indentation: the 'text-indent' property

   'text-indent'

          Value:            <length> | <percentage> | inherit
          Initial:          0
          Applies to:       block containers
          Inherited:        yes
          Percentages:      refer to width of containing block
          Media:            visual
          Computed value:   the percentage as specified or the absolute length

   This property specifies the indentation of the first line of text in a
   block container. More precisely, it specifies the indentation of the
   first box that flows into the block's first line box. The box is
   indented with respect to the left (or right, for right-to-left layout)
   edge of the line box. User agents must render this indentation as blank
   space.

   'Text-indent' only affects a line if it is the first formatted line of
   an element. For example, the first line of an anonymous block box is
   only affected if it is the first child of its parent element.

   Values have the following meanings:

   <length>
          The indentation is a fixed length.

   <percentage>
          The indentation is a percentage of the containing block width.

   The value of 'text-indent' may be negative, but there may be
   implementation-specific limits. If the value of 'text-indent' is either
   negative or exceeds the width of the block, that first box, described
   above, can overflow the block. The value of 'overflow' will affect
   whether such text that overflows the block is visible.

   Example(s):

   The following example causes a '3em' text indent.
p { text-indent: 3em }

   Note: Since the 'text-indent' property inherits, when specified on a
   block element, it will affect descendant inline-block elements. For
   this reason, it is often wise to specify 'text-indent: 0' on elements
   that are specified 'display:inline-block'.

16.2 Alignment: the 'text-align' property

   'text-align'

        Value:            left | right | center | justify | inherit
        Initial:          a nameless value that acts as 'left' if 'direction' is
                          'ltr', 'right' if 'direction' is 'rtl'
        Applies to:       block containers
        Inherited:        yes
        Percentages:      N/A
        Media:            visual
        Computed value:   the initial value or as specified

   This property describes how inline-level content of a block container
   is aligned. Values have the following meanings:

   left, right, center, justify
          Left, right, center, and justify text, respectively, as
          described in the section on inline formatting.

   A block of text is a stack of line boxes. In the case of 'left',
   'right' and 'center', this property specifies how the inline-level
   boxes within each line box align with respect to the line box's left
   and right sides; alignment is not with respect to the viewport. In the
   case of 'justify', this property specifies that the inline-level boxes
   are to be made flush with both sides of the line box if possible, by
   expanding or contracting the contents of inline boxes, else aligned as
   for the initial value. (See also 'letter-spacing' and 'word-spacing'.)

   If an element has a computed value for 'white-space' of 'pre' or
   'pre-wrap', then neither the glyphs of that element's text content nor
   its white space may be altered for the purpose of justification.

   Note: CSS may add a way to justify text with 'white-space: pre-wrap' in
   the future.

   Example(s):

   In this example, note that since 'text-align' is inherited, all
   block-level elements inside DIV elements with a class name of
   'important' will have their inline content centered.
div.important { text-align: center }

   Note. The actual justification algorithm used depends on the user-agent
   and the language/script of the text.

   Conforming user agents may interpret the value 'justify' as 'left' or
   'right', depending on whether the element's default writing direction
   is left-to-right or right-to-left, respectively.

16.3 Decoration

  16.3.1 Underlining, overlining, striking, and blinking: the 'text-decoration'
  property

   'text-decoration'

   Value:            none | [ underline || overline || line-through || blink ] |
                     inherit
   Initial:          none
   Applies to:       all elements
   Inherited:        no (see prose)
   Percentages:      N/A
   Media:            visual
   Computed value:   as specified

   This property describes decorations that are added to the text of an
   element using the element's color. When specified on or propagated to
   an inline element, it affects all the boxes generated by that element,
   and is further propagated to any in-flow block-level boxes that split
   the inline (see section 9.2.1.1). But, in CSS 2.1, it is undefined
   whether the decoration propagates into block-level tables. For block
   containers that establish an inline formatting context, the decorations
   are propagated to an anonymous inline element that wraps all the
   in-flow inline-level children of the block container. For all other
   elements it is propagated to any in-flow children. Note that text
   decorations are not propagated to floating and absolutely positioned
   descendants, nor to the contents of atomic inline-level descendants
   such as inline blocks and inline tables.

   Underlines, overlines, and line-throughs are applied only to text
   (including white space, letter spacing, and word spacing): margins,
   borders, and padding are skipped. User agents must not render these
   text decorations on content that is not text. For example, images and
   inline blocks must not be underlined.

   Note. If an element E has both 'visibility: hidden' and
   'text-decoration: underline', the underline is invisible (although any
   decoration of E's parent is visible.) However, CSS 2.1 does not specify
   if the underline is visible or invisible in E's children:
<span style="visibility: hidden; text-decoration: underline">
 <span style="visibility: visible">
  underlined or not?
 </span>
</span>

   This is expected to be specified in level 3 of CSS.

   The 'text-decoration' property on descendant elements cannot have any
   effect on the decoration of the ancestor. In determining the position
   of and thickness of text decoration lines, user agents may consider the
   font sizes of and dominant baselines of descendants, but must use the
   same baseline and thickness on each line. Relatively positioning a
   descendant moves all text decorations affecting it along with the
   descendant's text; it does not affect calculation of the decoration's
   initial position on that line.

   Values have the following meanings:

   none
          Produces no text decoration.

   underline
          Each line of text is underlined.

   overline
          Each line of text has a line above it.

   line-through
          Each line of text has a line through the middle.

   blink
          Text blinks (alternates between visible and invisible).
          Conforming user agents may simply not blink the text. Note that
          not blinking the text is one technique to satisfy checkpoint 3.3
          of WAI-UAAG.

   The color(s) required for the text decoration must be derived from the
   'color' property value of the element on which 'text-decoration' is
   set. The color of decorations must remain the same even if descendant
   elements have different 'color' values.

   Some user agents have implemented text-decoration by propagating the
   decoration to the descendant elements as opposed to preserving a
   constant thickness and line position as described above. This was
   arguably allowed by the looser wording in CSS2. SVG1, CSS1-only, and
   CSS2-only user agents may implement the older model and still claim
   conformance to this part of CSS 2.1. (This does not apply to UAs
   developed after this specification was released.)

   Example(s):

   In the following example for HTML, the text content of all A elements
   acting as hyperlinks (whether visited or not) will be underlined:
a:visited,a:link { text-decoration: underline }

   Example(s):

   In the following style sheet and document fragment:
   blockquote { text-decoration: underline; color: blue; }
   em { display: block; }
   cite { color: fuchsia; }

   <blockquote>
    <p>
     <span>
      Help, help!
      <em> I am under a hat! </em>
      <cite> —GwieF </cite>
     </span>
    </p>
   </blockquote>

   ...the underlining for the blockquote element is propagated to an
   anonymous inline element that surrounds the span element, causing the
   text "Help, help!" to be blue, with the blue underlining from the
   anonymous inline underneath it, the color being taken from the
   blockquote element. The <em>text</em> in the em block is also
   underlined, as it is in an in-flow block to which the underline is
   propagated. The final line of text is fuchsia, but the underline
   underneath it is still the blue underline from the anonymous inline
   element.

   Sample rendering of the above underline example

   This diagram shows the boxes involved in the example above. The rounded
   aqua line represents the anonymous inline element wrapping the inline
   contents of the paragraph element, the rounded blue line represents the
   span element, and the orange lines represent the blocks.

16.4 Letter and word spacing: the 'letter-spacing' and 'word-spacing' properties

   'letter-spacing'

          Value:            normal | <length> | inherit
          Initial:          normal
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   'normal' or absolute length

   This property specifies spacing behavior between text characters.
   Values have the following meanings:

   normal
          The spacing is the normal spacing for the current font. This
          value allows the user agent to alter the space between
          characters in order to justify text.

   <length>
          This value indicates inter-character space in addition to the
          default space between characters. Values may be negative, but
          there may be implementation-specific limits. User agents may not
          further increase or decrease the inter-character space in order
          to justify text.

   Character spacing algorithms are user agent-dependent.

   Example(s):

   In this example, the space between characters in BLOCKQUOTE elements is
   increased by '0.1em'.
blockquote { letter-spacing: 0.1em }

   In the following example, the user agent is not permitted to alter
   inter-character space:
blockquote { letter-spacing: 0cm }   /* Same as '0' */

   When the resultant space between two characters is not the same as the
   default space, user agents should not use ligatures.

   'word-spacing'

          Value:            normal | <length> | inherit
          Initial:          normal
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   for 'normal' the value '0'; otherwise the absolute
                            length

   This property specifies spacing behavior between words. Values have the
   following meanings:

   normal
          The normal inter-word space, as defined by the current font
          and/or the UA.

   <length>
          This value indicates inter-word space in addition to the default
          space between words. Values may be negative, but there may be
          implementation-specific limits.

   Word spacing algorithms are user agent-dependent. Word spacing is also
   influenced by justification (see the 'text-align' property). Word
   spacing affects each space (U+0020) and non-breaking space (U+00A0),
   left in the text after the white space processing rules have been
   applied. The effect of the property on other word-separator characters
   is undefined. However general punctuation, characters with zero advance
   width (such as the zero with space U+200B) and fixed-width spaces (such
   as U+3000 and U+2000 through U+200A) are not affected.

   Example(s):

   In this example, the word-spacing between each word in H1 elements is
   increased by '1em'.
h1 { word-spacing: 1em }

16.5 Capitalization: the 'text-transform' property

   'text-transform'

          Value:            capitalize | uppercase | lowercase | none | inherit
          Initial:          none
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property controls capitalization effects of an element's text.
   Values have the following meanings:

   capitalize
          Puts the first character of each word in uppercase; other
          characters are unaffected.

   uppercase
          Puts all characters of each word in uppercase.

   lowercase
          Puts all characters of each word in lowercase.

   none
          No capitalization effects.

   The actual transformation in each case is written language dependent.
   See BCP 47 ([BCP47]) for ways to find the language of an element.

   Only characters belonging to "bicameral scripts" [UNICODE] are
   affected.

   Example(s):

   In this example, all text in an H1 element is transformed to uppercase
   text.
h1 { text-transform: uppercase }

16.6 White space: the 'white-space' property

   'white-space'

         Value:            normal | pre | nowrap | pre-wrap | pre-line | inherit
         Initial:          normal
         Applies to:       all elements
         Inherited:        yes
         Percentages:      N/A
         Media:            visual
         Computed value:   as specified

   This property declares how white space inside the element is handled.
   Values have the following meanings:

   normal
          This value directs user agents to collapse sequences of white
          space, and break lines as necessary to fill line boxes.

   pre
          This value prevents user agents from collapsing sequences of
          white space. Lines are only broken at preserved newline
          characters.

   nowrap
          This value collapses white space as for 'normal', but suppresses
          line breaks within text.

   pre-wrap
          This value prevents user agents from collapsing sequences of
          white space. Lines are broken at preserved newline characters,
          and as necessary to fill line boxes.

   pre-line
          This value directs user agents to collapse sequences of white
          space. Lines are broken at preserved newline characters, and as
          necessary to fill line boxes.

   Newlines in the source can be represented by a carriage return
   (U+000D), a linefeed (U+000A) or both (U+000D U+000A) or by some other
   mechanism that identifies the beginning and end of document segments,
   such as the SGML RECORD-START and RECORD-END tokens. The CSS
   'white-space' processing model assumes all newlines have been
   normalized to line feeds. UAs that recognize other newline
   representations must apply the white space processing rules as if this
   normalization has taken place. If no newline rules are specified for
   the document language, each carriage return (U+000D) and CRLF sequence
   (U+000D U+000A) in the document text is treated as single line feed
   character. This default normalization rule also applies to generated
   content.

   UAs must recognize line feeds (U+000A) as newline characters. UAs may
   additionally treat other forced break characters as newline characters
   per UAX14.

   Example(s):

   The following examples show what white space behavior is expected from
   the PRE and P elements and the "nowrap" attribute in HTML.
pre        { white-space: pre }
p          { white-space: normal }
td[nowrap] { white-space: nowrap }

   In addition, the effect of an HTML PRE element with the non-standard
   "wrap" attribute is demonstrated by the following example:
pre[wrap]  { white-space: pre-wrap }

  16.6.1 The 'white-space' processing model

   For each inline element (including anonymous inline elements), the
   following steps are performed, treating bidi formatting characters as
   if they were not there:
    1. Each tab (U+0009), carriage return (U+000D), or space (U+0020)
       character surrounding a linefeed (U+000A) character is removed if
       'white-space' is set to 'normal', 'nowrap', or 'pre-line'.
    2. If 'white-space' is set to 'pre' or 'pre-wrap', any sequence of
       spaces (U+0020) unbroken by an element boundary is treated as a
       sequence of non-breaking spaces. However, for 'pre-wrap', a line
       breaking opportunity exists at the end of the sequence.
    3. If 'white-space' is set to 'normal' or 'nowrap', linefeed
       characters are transformed for rendering purpose into one of the
       following characters: a space character, a zero width space
       character (U+200B), or no character (i.e., not rendered), according
       to UA-specific algorithms based on the content script.
    4. If 'white-space' is set to 'normal', 'nowrap', or 'pre-line',
         1. every tab (U+0009) is converted to a space (U+0020)
         2. any space (U+0020) following another space (U+0020) — even a
            space before the inline, if that space also has 'white-space'
            set to 'normal', 'nowrap' or 'pre-line' — is removed.

   Then, the block container's inlines are laid out. Inlines are laid out,
   taking bidi reordering into account, and wrapping as specified by the
   'white-space' property. When wrapping, line breaking opportunities are
   determined based on the text prior to the white space collapsing steps
   above.

   As each line is laid out,
    1. If a space (U+0020) at the beginning of a line has 'white-space'
       set to 'normal', 'nowrap', or 'pre-line', it is removed.
    2. All tabs (U+0009) are rendered as a horizontal shift that lines up
       the start edge of the next glyph with the next tab stop. Tab stops
       occur at points that are multiples of 8 times the width of a space
       (U+0020) rendered in the block's font from the block's starting
       content edge.
    3. If a space (U+0020) at the end of a line has 'white-space' set to
       'normal', 'nowrap', or 'pre-line', it is also removed.
    4. If spaces (U+0020) or tabs (U+0009) at the end of a line have
       'white-space' set to 'pre-wrap', UAs may visually collapse them.

   Floated and absolutely-positioned elements do not introduce a line
   breaking opportunity.

   Note. CSS 2.1 does not fully define where line breaking opportunities
   occur.

  16.6.2 Example of bidirectionality with white space collapsing

   Given the following markup fragment, taking special note of spaces
   (with varied backgrounds and borders for emphasis and identification):

     <ltr>A <rtl> B </rtl> C</ltr>


   ...where the <ltr> element represents a left-to-right embedding and the
   <rtl> element represents a right-to-left embedding, and assuming that
   the 'white-space' property is set to 'normal', the above processing
   model would result in the following:
     * The space before the B ( ) would collapse with the space after the
       A ( ).
     * The space before the C ( ) would collapse with the space after the
       B ( ).

   This would leave two spaces, one after the A in the left-to-right
   embedding level, and one after the B in the right-to-left embedding
   level. This is then rendered according to the Unicode bidirectional
   algorithm, with the end result being:

     A  BC


   Note that there are two spaces between A and B, and none between B and
   C. This can sometimes be avoided by using the natural bidirectionality
   of characters instead of explicit embedding levels. Also, it is good to
   avoid spaces immediately inside start and end tags, as these tend to do
   weird things when dealing with white space collapsing.

  16.6.3 Control and combining characters' details

   Control characters other than U+0009 (tab), U+000A (line feed), U+0020
   (space), and U+202x (bidi formatting characters) are treated as
   characters to render in the same way as any normal character.

   Combining characters should be treated as part of the character with
   which they are supposed to combine. For example, :first-letter styles
   the entire glyph if you have content like "o<span>&#x308;</span>"; it
   does not just match the base character.

                                   17 Tables

   Contents
     * 17.1 Introduction to tables
     * 17.2 The CSS table model
          + 17.2.1 Anonymous table objects
     * 17.3 Columns
     * 17.4 Tables in the visual formatting model
          + 17.4.1 Caption position and alignment
     * 17.5 Visual layout of table contents
          + 17.5.1 Table layers and transparency
          + 17.5.2 Table width algorithms: the 'table-layout' property
               o 17.5.2.1 Fixed table layout
               o 17.5.2.2 Automatic table layout
          + 17.5.3 Table height algorithms
          + 17.5.4 Horizontal alignment in a column
          + 17.5.5 Dynamic row and column effects
     * 17.6 Borders
          + 17.6.1 The separated borders model
               o 17.6.1.1 Borders and Backgrounds around empty cells: the
                 'empty-cells' property
          + 17.6.2 The collapsing border model
               o 17.6.2.1 Border conflict resolution
          + 17.6.3 Border styles

17.1 Introduction to tables

   This chapter defines the processing model for tables in CSS. Part of
   this processing model is the layout. For the layout, this chapter
   introduces two algorithms; the first, the fixed table layout algorithm,
   is well-defined, but the second, the automatic table layout algorithm,
   is not fully defined by this specification.

   For the automatic table layout algorithm, some widely deployed
   implementations have achieved relatively close interoperability.

   Table layout can be used to represent tabular relationships between
   data. Authors specify these relationships in the document language and
   can specify their presentation using CSS 2.1.

   In a visual medium, CSS tables can also be used to achieve specific
   layouts. In this case, authors should not use table-related elements in
   the document language, but should apply the CSS to the relevant
   structural elements to achieve the desired layout.

   Authors may specify the visual formatting of a table as a rectangular
   grid of cells. Rows and columns of cells may be organized into row
   groups and column groups. Rows, columns, row groups, column groups, and
   cells may have borders drawn around them (there are two border models
   in CSS 2.1). Authors may align data vertically or horizontally within a
   cell and align data in all cells of a row or column.

   Example(s):

   Here is a simple three-row, three-column table described in HTML 4:
<TABLE>
<CAPTION>This is a simple 3x3 table</CAPTION>
<TR id="row1">
   <TH>Header 1  <TD>Cell 1  <TD>Cell 2
<TR id="row2">
   <TH>Header 2  <TD>Cell 3  <TD>Cell 4
<TR id="row3">
   <TH>Header 3  <TD>Cell 5  <TD>Cell 6
</TABLE>

   This code creates one table (the TABLE element), three rows (the TR
   elements), three header cells (the TH elements), and six data cells
   (the TD elements). Note that the three columns of this example are
   specified implicitly: there are as many columns in the table as
   required by header and data cells.

   The following CSS rule centers the text horizontally in the header
   cells and presents the text in the header cells with a bold font
   weight:
th { text-align: center; font-weight: bold }

   The next rules align the text of the header cells on their baseline and
   vertically center the text in each data cell:
th { vertical-align: baseline }
td { vertical-align: middle }

   The next rules specify that the top row will be surrounded by a 3px
   solid blue border and each of the other rows will be surrounded by a
   1px solid black border:
table   { border-collapse: collapse }
tr#row1 { border: 3px solid blue }
tr#row2 { border: 1px solid black }
tr#row3 { border: 1px solid black }

   Note, however, that the borders around the rows overlap where the rows
   meet. What color (black or blue) and thickness (1px or 3px) will the
   border between row1 and row2 be? We discuss this in the section on
   border conflict resolution.

   The following rule puts the table caption above the table:
caption { caption-side: top }

   The preceding example shows how CSS works with HTML 4 elements; in HTML
   4, the semantics of the various table elements (TABLE, CAPTION, THEAD,
   TBODY, TFOOT, COL, COLGROUP, TH, and TD) are well-defined. In other
   document languages (such as XML applications), there may not be
   pre-defined table elements. Therefore, CSS 2.1 allows authors to "map"
   document language elements to table elements via the 'display'
   property. For example, the following rule makes the FOO element act
   like an HTML TABLE element and the BAR element act like a CAPTION
   element:
FOO { display : table }
BAR { display : table-caption }

   We discuss the various table elements in the following section. In this
   specification, the term table element refers to any element involved in
   the creation of a table. An internal table element is one that produces
   a row, row group, column, column group, or cell.

17.2 The CSS table model

   The CSS table model is based on the HTML4 table model, in which the
   structure of a table closely parallels the visual layout of the table.
   In this model, a table consists of an optional caption and any number
   of rows of cells. The table model is said to be "row primary" since
   authors specify rows, not columns, explicitly in the document language.
   Columns are derived once all the rows have been specified -- the first
   cell of each row belongs to the first column, the second to the second
   column, etc.). Rows and columns may be grouped structurally and this
   grouping reflected in presentation (e.g., a border may be drawn around
   a group of rows).

   Thus, the table model consists of tables, captions, rows, row groups
   (including header groups and footer groups), columns, column groups,
   and cells.

   The CSS model does not require that the document language include
   elements that correspond to each of these components. For document
   languages (such as XML applications) that do not have pre-defined table
   elements, authors must map document language elements to table
   elements; this is done with the 'display' property. The following
   'display' values assign table formatting rules to an arbitrary element:

   table (In HTML: TABLE)
          Specifies that an element defines a block-level table: it is a
          rectangular block that participates in a block formatting
          context.

   inline-table (In HTML: TABLE)
          Specifies that an element defines an inline-level table: it is a
          rectangular block that participates in an inline formatting
          context).

   table-row (In HTML: TR)
          Specifies that an element is a row of cells.

   table-row-group (In HTML: TBODY)
          Specifies that an element groups one or more rows.

   table-header-group (In HTML: THEAD)
          Like 'table-row-group', but for visual formatting, the row group
          is always displayed before all other rows and row groups and
          after any top captions. Print user agents may repeat header rows
          on each page spanned by a table. If a table contains multiple
          elements with 'display: table-header-group', only the first is
          rendered as a header; the others are treated as if they had
          'display: table-row-group'.

   table-footer-group (In HTML: TFOOT)
          Like 'table-row-group', but for visual formatting, the row group
          is always displayed after all other rows and row groups and
          before any bottom captions. Print user agents may repeat footer
          rows on each page spanned by a table. If a table contains
          multiple elements with 'display: table-footer-group', only the
          first is rendered as a footer; the others are treated as if they
          had 'display: table-row-group'.

   table-column (In HTML: COL)
          Specifies that an element describes a column of cells.

   table-column-group (In HTML: COLGROUP)
          Specifies that an element groups one or more columns.

   table-cell (In HTML: TD, TH)
          Specifies that an element represents a table cell.

   table-caption (In HTML: CAPTION)
          Specifies a caption for the table. All elements with 'display:
          table-caption' must be rendered, as described in section 17.4.

   Replaced elements with these 'display' values are treated as their
   given display types during layout. For example, an image that is set to
   'display: table-cell' will fill the available cell space, and its
   dimensions might contribute towards the table sizing algorithms, as
   with an ordinary cell.

   Elements with 'display' set to 'table-column' or 'table-column-group'
   are not rendered (exactly as if they had 'display: none'), but they are
   useful, because they may have attributes which induce a certain style
   for the columns they represent.

   The default style sheet for HTML4 in the appendix illustrates the use
   of these values for HTML4:
table    { display: table }
tr       { display: table-row }
thead    { display: table-header-group }
tbody    { display: table-row-group }
tfoot    { display: table-footer-group }
col      { display: table-column }
colgroup { display: table-column-group }
td, th   { display: table-cell }
caption  { display: table-caption }

   User agents may ignore these 'display' property values for HTML table
   elements, since HTML tables may be rendered using other algorithms
   intended for backwards compatible rendering. However, this is not meant
   to discourage the use of 'display: table' on other, non-table elements
   in HTML.

  17.2.1 Anonymous table objects

   Document languages other than HTML may not contain all the elements in
   the CSS 2.1 table model. In these cases, the "missing" elements must be
   assumed in order for the table model to work. Any table element will
   automatically generate necessary anonymous table objects around itself,
   consisting of at least three nested objects corresponding to a
   'table'/'inline-table' element, a 'table-row' element, and a
   'table-cell' element. Missing elements generate anonymous objects
   (e.g., anonymous boxes in visual table layout) according to the
   following rules:

   For the purposes of these rules, the following terms are defined:

   row group box
          A 'table-row-group', 'table-header-group', or
          'table-footer-group'

   proper table child
          A 'table-row' box, row group box, 'table-column' box,
          'table-column-group' box, or 'table-caption' box.

   proper table row parent
          A 'table' or 'inline-table' box or row group box

   internal table box
          A 'table-cell' box, 'table-row' box, row group box,
          'table-column' box, or 'table-column-group' box.

   tabular container
          A 'table-row' box or proper table row parent

   consecutive
          Two sibling boxes are consecutive if they have no intervening
          siblings other than, optionally, an anonymous inline containing
          only white spaces. A sequence of sibling boxes is consecutive if
          each box in the sequence is consecutive to the one before it in
          the sequence.

   For the purposes of these rules, out-of-flow elements are represented
   as inline elements of zero width and height. Their containing blocks
   are chosen accordingly.

   The following steps are performed in three stages.
    1. Remove irrelevant boxes:
         1. All child boxes of a 'table-column' parent are treated as if
            they had 'display: none'.
         2. If a child C of a 'table-column-group' parent is not a
            'table-column' box, then it is treated as if it had 'display:
            none'.
         3. If a child C of a tabular container P is an anonymous inline
            box that contains only white space, and its immediately
            preceding and following siblings, if any, are proper table
            descendants of P and are either 'table-caption' or internal
            table boxes, then it is treated as if it had 'display: none'.
            A box D is a proper table descendant of A if D can be a
            descendant of A without causing the generation of any
            intervening 'table' or 'inline-table' boxes.
         4. If a box B is an anonymous inline containing only white space,
            and is between two immediate siblings each of which is either
            an internal table box or a 'table-caption' box then B is
            treated as if it had 'display: none'.
    2. Generate missing child wrappers:
         1. If a child C of a 'table' or 'inline-table' box is not a
            proper table child, then generate an anonymous 'table-row' box
            around C and all consecutive siblings of C that are not proper
            table children.
         2. If a child C of a row group box is not a 'table-row' box, then
            generate an anonymous 'table-row' box around C and all
            consecutive siblings of C that are not 'table-row' boxes.
         3. If a child C of a 'table-row' box is not a 'table-cell', then
            generate an anonymous 'table-cell' box around C and all
            consecutive siblings of C that are not 'table-cell' boxes.
    3. Generate missing parents:
         1. For each 'table-cell' box C in a sequence of consecutive
            internal table and 'table-caption' siblings, if C's parent is
            not a 'table-row' then generate an anonymous 'table-row' box
            around C and all consecutive siblings of C that are
            'table-cell' boxes.
         2. For each proper table child C in a sequence of consecutive
            proper table children, if C is misparented then generate an
            anonymous 'table' or 'inline-table' box T around C and all
            consecutive siblings of C that are proper table children. (If
            C's parent is an 'inline' box, then T must be an
            'inline-table' box; otherwise it must be a 'table' box.)
               o A 'table-row' is misparented if its parent is neither a
                 row group box nor a 'table' or 'inline-table' box.
               o A 'table-column' box is misparented if its parent is
                 neither a 'table-column-group' box nor a 'table' or
                 'inline-table' box.
               o A row group box, 'table-column-group' box, or
                 'table-caption' box is misparented if its parent is
                 neither a 'table' box nor an 'inline-table' box.

   Example(s):

   In this XML example, a 'table' element is assumed to contain the HBOX
   element:
<HBOX>
  <VBOX>George</VBOX>
  <VBOX>4287</VBOX>
  <VBOX>1998</VBOX>
</HBOX>

   because the associated style sheet is:
HBOX { display: table-row }
VBOX { display: table-cell }

   Example(s):

   In this example, three 'table-cell' elements are assumed to contain the
   text in the ROWs. Note that the text is further encapsulated in
   anonymous inline boxes, as explained in visual formatting model:
<STACK>
  <ROW>This is the <D>top</D> row.</ROW>
  <ROW>This is the <D>middle</D> row.</ROW>
  <ROW>This is the <D>bottom</D> row.</ROW>
</STACK>

   The style sheet is:
STACK { display: inline-table }
ROW   { display: table-row }
D     { display: inline; font-weight: bolder }

17.3 Columns

   Table cells may belong to two contexts: rows and columns. However, in
   the source document cells are descendants of rows, never of columns.
   Nevertheless, some aspects of cells can be influenced by setting
   properties on columns.

   The following properties apply to column and column-group elements:

   'border'
          The various border properties apply to columns only if
          'border-collapse' is set to 'collapse' on the table element. In
          that case, borders set on columns and column groups are input to
          the conflict resolution algorithm that selects the border styles
          at every cell edge.

   'background'
          The background properties set the background for cells in the
          column, but only if both the cell and row have transparent
          backgrounds. See "Table layers and transparency."

   'width'
          The 'width' property gives the minimum width for the column.

   'visibility'
          If the 'visibility' of a column is set to 'collapse', none of
          the cells in the column are rendered, and cells that span into
          other columns are clipped. In addition, the width of the table
          is diminished by the width the column would have taken up. See
          "Dynamic effects" below. Other values for 'visibility' have no
          effect.

   Example(s):

   Here are some examples of style rules that set properties on columns.
   The first two rules together implement the "rules" attribute of HTML 4
   with a value of "cols". The third rule makes the "totals" column blue,
   the final two rules shows how to make a column a fixed size, by using
   the fixed layout algorithm.
col { border-style: none solid }
table { border-style: hidden }
col.totals { background: blue }
table { table-layout: fixed }
col.totals { width: 5em }

17.4 Tables in the visual formatting model

   In terms of the visual formatting model, a table can behave like a
   block-level (for 'display: table') or inline-level (for 'display:
   inline-table') element.

   In both cases, the table generates a principal block box called the
   table wrapper box that contains the table box itself and any caption
   boxes (in document order). The table box is a block-level box that
   contains the table's internal table boxes. The caption boxes are
   block-level boxes that retain their own content, padding, margin, and
   border areas, and are rendered as normal block boxes inside the table
   wrapper box. Whether the caption boxes are placed before or after the
   table box is decided by the 'caption-side' property, as described
   below.

   The table wrapper box is a 'block' box if the table is block-level, and
   an 'inline-block' box if the table is inline-level. The table wrapper
   box establishes a block formatting context. The table box (not the
   table wrapper box) is used when doing baseline vertical alignment for
   an 'inline-table'. The width of the table wrapper box is the
   border-edge width of the table box inside it, as described by section
   17.5.2. Percentages on 'width' and 'height' on the table are relative
   to the table wrapper box's containing block, not the table wrapper box
   itself.

   The computed values of properties 'position', 'float', 'margin-*',
   'top', 'right', 'bottom', and 'left' on the table element are used on
   the table wrapper box and not the table box; all other values of
   non-inheritable properties are used on the table box and not the table
   wrapper box. (Where the table element's values are not used on the
   table and table wrapper boxes, the initial values are used instead.)

   A table with a caption above it

   Diagram of a table with a caption above it.

  17.4.1 Caption position and alignment

   'caption-side'

          Value:            top | bottom | inherit
          Initial:          top
          Applies to:       'table-caption' elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property specifies the position of the caption box with respect to
   the table box. Values have the following meanings:

   top
          Positions the caption box above the table box.

   bottom
          Positions the caption box below the table box.

   Note: CSS2 described a different width and horizontal alignment
   behavior. That behavior will be introduced in CSS3 using the values
   'top-outside' and 'bottom-outside' on this property.

   To align caption content horizontally within the caption box, use the
   'text-align' property.

   Example(s):

   In this example, the 'caption-side' property places captions below
   tables. The caption will be as wide as the parent of the table, and
   caption text will be left-justified.
caption { caption-side: bottom;
          width: auto;
          text-align: left }

17.5 Visual layout of table contents

   Internal table elements generate rectangular boxes with content and
   borders. Cells have padding as well. Internal table elements do not
   have margins.

   The visual layout of these boxes is governed by a rectangular,
   irregular grid of rows and columns. Each box occupies a whole number of
   grid cells, determined according to the following rules. These rules do
   not apply to HTML 4 or earlier HTML versions; HTML imposes its own
   limitations on row and column spans.
    1. Each row box occupies one row of grid cells. Together, the row
       boxes fill the table from top to bottom in the order they occur in
       the source document (i.e., the table occupies exactly as many grid
       rows as there are row elements).
    2. A row group occupies the same grid cells as the rows it contains.
    3. A column box occupies one or more columns of grid cells. Column
       boxes are placed next to each other in the order they occur. The
       first column box may be either on the left or on the right,
       depending on the value of the 'direction' property of the table.
    4. A column group box occupies the same grid cells as the columns it
       contains.
    5. Cells may span several rows or columns. (Although CSS 2.1 does not
       define how the number of spanned rows or columns is determined, a
       user agent may have special knowledge about the source document; a
       future update of CSS may provide a way to express this knowledge in
       CSS syntax.) Each cell is thus a rectangular box, one or more grid
       cells wide and high. The top row of this rectangle is in the row
       specified by the cell's parent. The rectangle must be as far to the
       left as possible, but the part of the cell in the first column it
       occupies must not overlap with any other cell box (i.e., a
       row-spanning cell starting in a prior row), and the cell must be to
       the right of all cells in the same row that are earlier in the
       source document. If this position would cause a column-spanning
       cell to overlap a row-spanning cell from a prior row, CSS does not
       define the results: implementations may either overlap the cells
       (as is done in many HTML implementations) or may shift the later
       cell to the right to avoid such overlap. (This constraint holds if
       the 'direction' property of the table is 'ltr'; if the 'direction'
       is 'rtl', interchange "left" and "right" in the previous two
       sentences.)
    6. A cell box cannot extend beyond the last row box of a table or row
       group; the user agents must shorten it until it fits.

   The edges of the rows, columns, row groups and column groups in the
   collapsing borders model coincide with the hypothetical grid lines on
   which the borders of the cells are centered. (And thus, in this model,
   the rows together exactly cover the table, leaving no gaps; ditto for
   the columns.) In the separated borders model, the edges coincide with
   the border edges of cells. (And thus, in this model, there may be gaps
   between the rows, columns, row groups or column groups, corresponding
   to the 'border-spacing' property.)

   Note. Positioning and floating of table cells can cause them not to be
   table cells anymore, according to the rules in section 9.7. When
   floating is used, the rules on anonymous table objects may cause an
   anonymous cell object to be created as well.

   Here is an example illustrating rule 5. The following illegal (X)HTML
   snippet defines conflicting cells:
<table>
<tr><td>1 </td><td rowspan="2">2 </td><td>3 </td><td>4 </td></tr>
<tr><td colspan="2">5 </td></tr>
</table>

   User agents are free to visually overlap the cells, as in the figure on
   the left, or to shift the cell to avoid the visual overlap, as in the
   figure on the right.

   One table with overlapping cells and one without    [D]

   Two possible renderings of an erroneous HTML table.

  17.5.1 Table layers and transparency

   For the purposes of finding the background of each table cell, the
   different table elements may be thought of as being on six superimposed
   layers. The background set on an element in one of the layers will only
   be visible if the layers above it have a transparent background.

   schema of table layers    [D]

   Schema of table layers.

    1. The lowest layer is a single plane, representing the table box
       itself. Like all boxes, it may be transparent.
    2. The next layer contains the column groups. Each column group
       extends from the top of the cells in the top row to the bottom of
       the cells on the bottom row and from the left edge of its leftmost
       column to the right edge of its rightmost column. The background
       covers exactly the full area of all cells that originate in the
       column group, even if they span outside the column group, but this
       difference in area does not affect background image positioning.
    3. On top of the column groups are the areas representing the column
       boxes. Each column is as tall as the column groups and as wide as a
       normal (single-column-spanning) cell in the column. The background
       covers exactly the full area of all cells that originate in the
       column, even if they span outside the column, but this difference
       in area does not affect background image positioning.
    4. Next is the layer containing the row groups. Each row group extends
       from the top left corner of its topmost cell in the first column to
       the bottom right corner of its bottommost cell in the last column.
    5. The next to last layer contains the rows. Each row is as wide as
       the row groups and as tall as a normal (single-row-spanning) cell
       in the row. As with columns, the background covers exactly the full
       area of all cells that originate in the row, even if they span
       outside the row, but this difference in area does not affect
       background image positioning.
    6. The topmost layer contains the cells themselves. As the figure
       shows, although all rows contain the same number of cells, not
       every cell may have specified content. In the separated borders
       model ('border-collapse' is 'separate'), if the value of their
       'empty-cells' property is 'hide' these "empty" cells are
       transparent through the cell, row, row group, column and column
       group backgrounds, letting the table background show through.

   A "missing cell" is a cell in the row/column grid that is not occupied
   by an element or pseudo-element. Missing cells are rendered as if an
   anonymous table-cell box occupied their position in the grid.

   In the following example, the first row contains four non-empty cells,
   but the second row contains only one non-empty cell, and thus the table
   background shines through, except where a cell from the first row spans
   into this row. The following HTML code and style rules
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<HTML>
  <HEAD>
    <TITLE>Table example</TITLE>
    <STYLE type="text/css">
      TABLE  { background: #ff0; border: solid black;
               empty-cells: hide }
      TR.top { background: red }
      TD     { border: solid black }
    </STYLE>
  </HEAD>
  <BODY>
    <TABLE>
      <TR CLASS="top">
        <TD> 1
        <TD rowspan="2"> 2
        <TD> 3
        <TD> 4
      <TR>
        <TD> 5
        <TD>
    </TABLE>
  </BODY>
</HTML>

   might be formatted as follows:

   Table with three empty cells in bottom row    [D]

   Table with empty cells in the bottom row.

   Note that if the table has 'border-collapse: separate', the background
   of the area given by the 'border-spacing' property is always the
   background of the table element. See the separated borders model.

  17.5.2 Table width algorithms: the 'table-layout' property

   CSS does not define an "optimal" layout for tables since, in many
   cases, what is optimal is a matter of taste. CSS does define
   constraints that user agents must respect when laying out a table. User
   agents may use any algorithm they wish to do so, and are free to prefer
   rendering speed over precision, except when the "fixed layout
   algorithm" is selected.

   Note that this section overrides the rules that apply to calculating
   widths as described in section 10.3. In particular, if the margins of a
   table are set to '0' and the width to 'auto', the table will not
   automatically size to fill its containing block. However, once the
   calculated value of 'width' for the table is found (using the
   algorithms given below or, when appropriate, some other UA dependent
   algorithm) then the other parts of section 10.3 do apply. Therefore a
   table can be centered using left and right 'auto' margins, for
   instance.

   Future updates of CSS may introduce ways of making tables automatically
   fit their containing blocks.

   'table-layout'

          Value:            auto | fixed | inherit
          Initial:          auto
          Applies to:       'table' and 'inline-table' elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   The 'table-layout' property controls the algorithm used to lay out the
   table cells, rows, and columns. Values have the following meaning:

   fixed
          Use the fixed table layout algorithm

   auto
          Use any automatic table layout algorithm

   The two algorithms are described below.

    17.5.2.1 Fixed table layout

   With this (fast) algorithm, the horizontal layout of the table does not
   depend on the contents of the cells; it only depends on the table's
   width, the width of the columns, and borders or cell spacing.

   The table's width may be specified explicitly with the 'width'
   property. A value of 'auto' (for both 'display: table' and 'display:
   inline-table') means use the automatic table layout algorithm. However,
   if the table is a block-level table ('display: table') in normal flow,
   a UA may (but does not have to) use the algorithm of 10.3.3 to compute
   a width and apply fixed table layout even if the specified width is
   'auto'.

   Example(s):

   If a UA supports fixed table layout when 'width' is 'auto', the
   following will create a table that is 4em narrower than its containing
   block:
table { table-layout: fixed;
        margin-left: 2em;
        margin-right: 2em }

   In the fixed table layout algorithm, the width of each column is
   determined as follows:
    1. A column element with a value other than 'auto' for the 'width'
       property sets the width for that column.
    2. Otherwise, a cell in the first row with a value other than 'auto'
       for the 'width' property determines the width for that column. If
       the cell spans more than one column, the width is divided over the
       columns.
    3. Any remaining columns equally divide the remaining horizontal table
       space (minus borders or cell spacing).

   The width of the table is then the greater of the value of the 'width'
   property for the table element and the sum of the column widths (plus
   cell spacing or borders). If the table is wider than the columns, the
   extra space should be distributed over the columns.

   If a subsequent row has more columns than the greater of the number
   determined by the table-column elements and the number determined by
   the first row, then additional columns may not be rendered. CSS 2.1
   does not define the width of the columns and the table if they are
   rendered. When using 'table-layout: fixed', authors should not omit
   columns from the first row.

   In this manner, the user agent can begin to lay out the table once the
   entire first row has been received. Cells in subsequent rows do not
   affect column widths. Any cell that has content that overflows uses the
   'overflow' property to determine whether to clip the overflow content.

    17.5.2.2 Automatic table layout

   In this algorithm (which generally requires no more than two passes),
   the table's width is given by the width of its columns (and intervening
   borders). This algorithm reflects the behavior of several popular HTML
   user agents at the writing of this specification. UAs are not required
   to implement this algorithm to determine the table layout in the case
   that 'table-layout' is 'auto'; they can use any other algorithm even if
   it results in different behavior.

   Input to the automatic table layout must only include the width of the
   containing block and the content of, and any CSS properties set on, the
   table and any of its descendants.

   Note. This may be defined in more detail in CSS3.

   The remainder of this section is non-normative.

   This algorithm may be inefficient since it requires the user agent to
   have access to all the content in the table before determining the
   final layout and may demand more than one pass.

   Column widths are determined as follows:
    1. Calculate the minimum content width (MCW) of each cell: the
       formatted content may span any number of lines but may not overflow
       the cell box. If the specified 'width' (W) of the cell is greater
       than MCW, W is the minimum cell width. A value of 'auto' means that
       MCW is the minimum cell width.
       Also, calculate the "maximum" cell width of each cell: formatting
       the content without breaking lines other than where explicit line
       breaks occur.
    2. For each column, determine a maximum and minimum column width from
       the cells that span only that column. The minimum is that required
       by the cell with the largest minimum cell width (or the column
       'width', whichever is larger). The maximum is that required by the
       cell with the largest maximum cell width (or the column 'width',
       whichever is larger).
    3. For each cell that spans more than one column, increase the minimum
       widths of the columns it spans so that together, they are at least
       as wide as the cell. Do the same for the maximum widths. If
       possible, widen all spanned columns by approximately the same
       amount.
    4. For each column group element with a 'width' other than 'auto',
       increase the minimum widths of the columns it spans, so that
       together they are at least as wide as the column group's 'width'.

   This gives a maximum and minimum width for each column.

   The caption width minimum (CAPMIN) is determined by calculating for
   each caption the minimum caption outer width as the MCW of a
   hypothetical table cell that contains the caption formatted as
   "display: block". The greatest of the minimum caption outer widths is
   CAPMIN.

   Column and caption widths influence the final table width as follows:
    1. If the 'table' or 'inline-table' element's 'width' property has a
       computed value (W) other than 'auto', the used width is the greater
       of W, CAPMIN, and the minimum width required by all the columns
       plus cell spacing or borders (MIN). If the used width is greater
       than MIN, the extra width should be distributed over the columns.
    2. If the 'table' or 'inline-table' element has 'width: auto', the
       used width is the greater of the table's containing block width,
       CAPMIN, and MIN. However, if either CAPMIN or the maximum width
       required by the columns plus cell spacing or borders (MAX) is less
       than that of the containing block, use max(MAX, CAPMIN).

   A percentage value for a column width is relative to the table width.
   If the table has 'width: auto', a percentage represents a constraint on
   the column's width, which a UA should try to satisfy. (Obviously, this
   is not always possible: if the column's width is '110%', the constraint
   cannot be satisfied.)

   Note. In this algorithm, rows (and row groups) and columns (and column
   groups) both constrain and are constrained by the dimensions of the
   cells they contain. Setting the width of a column may indirectly
   influence the height of a row, and vice versa.

  17.5.3 Table height algorithms

   The height of a table is given by the 'height' property for the 'table'
   or 'inline-table' element. A value of 'auto' means that the height is
   the sum of the row heights plus any cell spacing or borders. Any other
   value is treated as a minimum height. CSS 2.1 does not define how extra
   space is distributed when the 'height' property causes the table to be
   taller than it otherwise would be.

   Note. Future updates of CSS may specify this further.

   The height of a 'table-row' element's box is calculated once the user
   agent has all the cells in the row available: it is the maximum of the
   row's computed 'height', the computed 'height' of each cell in the row,
   and the minimum height (MIN) required by the cells. A 'height' value of
   'auto' for a 'table-row' means the row height used for layout is MIN.
   MIN depends on cell box heights and cell box alignment (much like the
   calculation of a line box height). CSS 2.1 does not define how the
   height of table cells and table rows is calculated when their height is
   specified using percentage values. CSS 2.1 does not define the meaning
   of 'height' on row groups.

   In CSS 2.1, the height of a cell box is the minimum height required by
   the content. The table cell's 'height' property can influence the
   height of the row (see above), but it does not increase the height of
   the cell box.

   CSS 2.1 does not specify how cells that span more than one row affect
   row height calculations except that the sum of the row heights involved
   must be great enough to encompass the cell spanning the rows.

   The 'vertical-align' property of each table cell determines its
   alignment within the row. Each cell's content has a baseline, a top, a
   middle, and a bottom, as does the row itself. In the context of tables,
   values for 'vertical-align' have the following meanings:

   baseline
          The baseline of the cell is put at the same height as the
          baseline of the first of the rows it spans (see below for the
          definition of baselines of cells and rows).

   top
          The top of the cell box is aligned with the top of the first row
          it spans.

   bottom
          The bottom of the cell box is aligned with the bottom of the
          last row it spans.

   middle
          The center of the cell is aligned with the center of the rows it
          spans.

   sub, super, text-top, text-bottom, <length>, <percentage>
          These values do not apply to cells; the cell is aligned at the
          baseline instead.

   The baseline of a cell is the baseline of the first in-flow line box in
   the cell, or the first in-flow table-row in the cell, whichever comes
   first. If there is no such line box or table-row, the baseline is the
   bottom of content edge of the cell box. For the purposes of finding a
   baseline, in-flow boxes with a scrolling mechanisms (see the 'overflow'
   property) must be considered as if scrolled to their origin position.
   Note that the baseline of a cell may end up below its bottom border,
   see the example below.

   The maximum distance between the top of the cell box and the baseline
   over all cells that have 'vertical-align: baseline' is used to set the
   baseline of the row. Here is an example:

   Example of vertically aligning the cells    [D]

   Diagram showing the effect of various values of 'vertical-align' on
   table cells.

   Cell boxes 1 and 2 are aligned at their baselines. Cell box 2 has the
   largest height above the baseline, so that determines the baseline of
   the row.

   If a row has no cell box aligned to its baseline, the baseline of that
   row is the bottom content edge of the lowest cell in the row.

   To avoid ambiguous situations, the alignment of cells proceeds in the
   following order:
    1. First the cells that are aligned on their baseline are positioned.
       This will establish the baseline of the row. Next the cells with
       'vertical-align: top' are positioned.
    2. The row now has a top, possibly a baseline, and a provisional
       height, which is the distance from the top to the lowest bottom of
       the cells positioned so far. (See conditions on the cell padding
       below.)
    3. If any of the remaining cells, those aligned at the bottom or the
       middle, have a height that is larger than the current height of the
       row, the height of the row will be increased to the maximum of
       those cells, by lowering the bottom.
    4. Finally the remaining cells are positioned.

   Cell boxes that are smaller than the height of the row receive extra
   top or bottom padding.

   The cell in this example has a baseline below its bottom border:
div { height: 0; overflow: hidden; }

<table>
 <tr>
  <td>
   <div> Test </div>
  </td>
 </tr>
</table>

  17.5.4 Horizontal alignment in a column

   The horizontal alignment of inline-level content within a cell box can
   be specified by the value of the 'text-align' property on the cell.

  17.5.5 Dynamic row and column effects

   The 'visibility' property takes the value 'collapse' for row, row
   group, column, and column group elements. This value causes the entire
   row or column to be removed from the display, and the space normally
   taken up by the row or column to be made available for other content.
   Contents of spanned rows and columns that intersect the collapsed
   column or row are clipped. The suppression of the row or column,
   however, does not otherwise affect the layout of the table. This allows
   dynamic effects to remove table rows or columns without forcing a
   re-layout of the table in order to account for the potential change in
   column constraints.

17.6 Borders

   There are two distinct models for setting borders on table cells in
   CSS. One is most suitable for so-called separated borders around
   individual cells, the other is suitable for borders that are continuous
   from one end of the table to the other. Many border styles can be
   achieved with either model, so it is often a matter of taste which one
   is used.

   'border-collapse'

          Value:            collapse | separate | inherit
          Initial:          separate
          Applies to:       'table' and 'inline-table' elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   This property selects a table's border model. The value 'separate'
   selects the separated borders border model. The value 'collapse'
   selects the collapsing borders model. The models are described below.

  17.6.1 The separated borders model

   'border-spacing'

          Value:            <length> <length>? | inherit
          Initial:          0
          Applies to:       'table' and 'inline-table' elements*
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   two absolute lengths

   *) Note: user agents may also apply the 'border-spacing' property to
   'frameset' elements. Which elements are 'frameset' elements is not
   defined by this specification and is up to the document language. For
   example, HTML4 defines a <FRAMESET> element, and XHTML 1.0 defines a
   <frameset> element. The 'border-spacing' property on a 'frameset'
   element can be thus used as a valid substitute for the non-standard
   'framespacing' attribute.

   The lengths specify the distance that separates adjoining cell borders.
   If one length is specified, it gives both the horizontal and vertical
   spacing. If two are specified, the first gives the horizontal spacing
   and the second the vertical spacing. Lengths may not be negative.

   The distance between the table border and the borders of the cells on
   the edge of the table is the table's padding for that side, plus the
   relevant border spacing distance. For example, on the right hand side,
   the distance is padding-right + horizontal border-spacing.

   The width of the table is the distance from the left inner padding edge
   to the right inner padding edge (including the border spacing but
   excluding padding and border).

   However, in HTML and XHTML1, the width of the <table> element is the
   distance from the left border edge to the right border edge.

   Note: In CSS3 this peculiar requirement will be defined in terms of UA
   style sheet rules and the 'box-sizing' property.

   In this model, each cell has an individual border. The 'border-spacing'
   property specifies the distance between the borders of adjoining cells.
   In this space, the row, column, row group, and column group backgrounds
   are invisible, allowing the table background to show through. Rows,
   columns, row groups, and column groups cannot have borders (i.e., user
   agents must ignore the border properties for those elements).

   Example(s):

   The table in the figure below could be the result of a style sheet like
   this:
table      { border: outset 10pt;
             border-collapse: separate;
             border-spacing: 15pt }
td         { border: inset 5pt }
td.special { border: inset 10pt }  /* The top-left cell */

   A table with border-spacing    [D]

   A table with 'border-spacing' set to a length value. Note that each
   cell has its own border, and the table has a separate border as well.

    17.6.1.1 Borders and Backgrounds around empty cells: the 'empty-cells'
    property

   'empty-cells'

          Value:            show | hide | inherit
          Initial:          show
          Applies to:       'table-cell' elements
          Inherited:        yes
          Percentages:      N/A
          Media:            visual
          Computed value:   as specified

   In the separated borders model, this property controls the rendering of
   borders and backgrounds around cells that have no visible content.
   Empty cells and cells with the 'visibility' property set to 'hidden'
   are considered to have no visible content. Cells are empty unless they
   contain one or more of the following:
     * floating content (including empty elements),
     * in-flow content (including empty elements) other than white space
       that has been collapsed away by the 'white-space' property
       handling.

   When this property has the value 'show', borders and backgrounds are
   drawn around/behind empty cells (like normal cells).

   A value of 'hide' means that no borders or backgrounds are drawn
   around/behind empty cells (see point 6 in 17.5.1). Furthermore, if all
   the cells in a row have a value of 'hide' and have no visible content,
   then the row has zero height and there is vertical border-spacing on
   only one side of the row.

   Example(s):

   The following rule causes borders and backgrounds to be drawn around
   all cells:
table { empty-cells: show }

  17.6.2 The collapsing border model

   In the collapsing border model, it is possible to specify borders that
   surround all or part of a cell, row, row group, column, and column
   group. Borders for HTML's "rules" attribute can be specified this way.

   Borders are centered on the grid lines between the cells. User agents
   must find a consistent rule for rounding off in the case of an odd
   number of discrete units (screen pixels, printer dots).

   The diagram below shows how the width of the table, the widths of the
   borders, the padding, and the cell width interact. Their relation is
   given by the following equation, which holds for every row of the
   table:

     row-width = (0.5 * border-width[0]) + padding-left[1] + width[1] +
     padding-right[1] + border-width[1] + padding-left[2] +...+
     padding-right[n] + (0.5 * border-width[n])

   Here n is the number of cells in the row, padding-left[i] and
   padding-right[i] refer to the left (resp., right) padding of cell i,
   and border-width[i] refers to the border between cells i and i + 1.

   UAs must compute an initial left and right border width for the table
   by examining the first and last cells in the first row of the table.
   The left border width of the table is half of the first cell's
   collapsed left border, and the right border width of the table is half
   of the last cell's collapsed right border. If subsequent rows have
   larger collapsed left and right borders, then any excess spills into
   the margin area of the table.

   The top border width of the table is computed by examining all cells
   who collapse their top borders with the top border of the table. The
   top border width of the table is equal to half of the maximum collapsed
   top border. The bottom border width is computed by examining all cells
   whose bottom borders collapse with the bottom of the table. The bottom
   border width is equal to half of the maximum collapsed bottom border.

   Any borders that spill into the margin are taken into account when
   determining if the table overflows some ancestor (see 'overflow').

   Schema showing the widths of cells and borders and the padding of cells
      [D]

   Schema showing the widths of cells and borders and the padding of
   cells.

   Note that in this model, the width of the table includes half the table
   border. Also, in this model, a table does not have padding (but does
   have margins).

   CSS 2.1 does not define where the edge of a background on a table
   element lies.

    17.6.2.1 Border conflict resolution

   In the collapsing border model, borders at every edge of every cell may
   be specified by border properties on a variety of elements that meet at
   that edge (cells, rows, row groups, columns, column groups, and the
   table itself), and these borders may vary in width, style, and color.
   The rule of thumb is that at each edge the most "eye catching" border
   style is chosen, except that any occurrence of the style 'hidden'
   unconditionally turns the border off.

   The following rules determine which border style "wins" in case of a
   conflict:
    1. Borders with the 'border-style' of 'hidden' take precedence over
       all other conflicting borders. Any border with this value
       suppresses all borders at this location.
    2. Borders with a style of 'none' have the lowest priority. Only if
       the border properties of all the elements meeting at this edge are
       'none' will the border be omitted (but note that 'none' is the
       default value for the border style.)
    3. If none of the styles are 'hidden' and at least one of them is not
       'none', then narrow borders are discarded in favor of wider ones.
       If several have the same 'border-width' then styles are preferred
       in this order: 'double', 'solid', 'dashed', 'dotted', 'ridge',
       'outset', 'groove', and the lowest: 'inset'.
    4. If border styles differ only in color, then a style set on a cell
       wins over one on a row, which wins over a row group, column, column
       group and, lastly, table. When two elements of the same type
       conflict, then the one further to the left (if the table's
       'direction' is 'ltr'; right, if it is 'rtl') and further to the top
       wins.

   Example(s):

   The following example illustrates the application of these precedence
   rules. This style sheet:
table          { border-collapse: collapse;
                 border: 5px solid yellow; }
*#col1         { border: 3px solid black; }
td             { border: 1px solid red; padding: 1em; }
td.cell5       { border: 5px dashed blue; }
td.cell6       { border: 5px solid green; }

   with this HTML source:
<TABLE>
<COL id="col1"><COL id="col2"><COL id="col3">
<TR id="row1">
    <TD> 1
    <TD> 2
    <TD> 3
</TR>
<TR id="row2">
    <TD> 4
    <TD class="cell5"> 5
    <TD class="cell6"> 6
</TR>
<TR id="row3">
    <TD> 7
    <TD> 8
    <TD> 9
</TR>
<TR id="row4">
    <TD> 10
    <TD> 11
    <TD> 12
</TR>
<TR id="row5">
    <TD> 13
    <TD> 14
    <TD> 15
</TR>
</TABLE>

   would produce something like this:

   An example of a table with collapsed borders    [D]

   An example of a table with collapsed borders.

   Example(s):

   Here is an example of hidden collapsing borders:

   Table with two omitted borders    [D]

   Table with two omitted internal borders.

   HTML source:
<TABLE style="border-collapse: collapse; border: solid;">
<TR><TD style="border-right: hidden; border-bottom: hidden">foo</TD>
    <TD style="border: solid">bar</TD></TR>
<TR><TD style="border: none">foo</TD>
    <TD style="border: solid">bar</TD></TR>
</TABLE>

  17.6.3 Border styles

   Some of the values of the 'border-style' have different meanings in
   tables than for other elements. In the list below they are marked with
   an asterisk.

   none
          No border.

   *hidden
          Same as 'none', but in the collapsing border model, also
          inhibits any other border (see the section on border conflicts).

   dotted
          The border is a series of dots.

   dashed
          The border is a series of short line segments.

   solid
          The border is a single line segment.

   double
          The border is two solid lines. The sum of the two lines and the
          space between them equals the value of 'border-width'.

   groove
          The border looks as though it were carved into the canvas.

   ridge
          The opposite of 'groove': the border looks as though it were
          coming out of the canvas.

   *inset
          In the separated borders model, the border makes the entire box
          look as though it were embedded in the canvas. In the collapsing
          border model, drawn the same as 'ridge'.

   *outset
          In the separated borders model, the border makes the entire box
          look as though it were coming out of the canvas. In the
          collapsing border model, drawn the same as 'groove'.

                               18 User interface

   Contents
     * 18.1 Cursors: the 'cursor' property
     * 18.2 System Colors
     * 18.3 User preferences for fonts
     * 18.4 Dynamic outlines: the 'outline' property
          + 18.4.1 Outlines and the focus
     * 18.5 Magnification

18.1 Cursors: the 'cursor' property

   'cursor'

   Value:   [ [<uri> ,]* [ auto | crosshair | default | pointer | move |
   e-resize | ne-resize | nw-resize | n-resize | se-resize | sw-resize |
   s-resize | w-resize | text | wait | help | progress ] ] | inherit
   Initial:   auto
   Applies to:   all elements
   Inherited:   yes
   Percentages:   N/A
   Media:   visual, interactive
   Computed value:   as specified, except with any relative URLs converted
   to absolute

   This property specifies the type of cursor to be displayed for the
   pointing device. Values have the following meanings:

   auto
          The UA determines the cursor to display based on the current
          context.

   crosshair
          A simple crosshair (e.g., short line segments resembling a "+"
          sign).

   default
          The platform-dependent default cursor. Often rendered as an
          arrow.

   pointer
          The cursor is a pointer that indicates a link.

   move
          Indicates something is to be moved.

   e-resize, ne-resize, nw-resize, n-resize, se-resize, sw-resize,
          s-resize, w-resize
          Indicate that some edge is to be moved. For example, the
          'se-resize' cursor is used when the movement starts from the
          south-east corner of the box.

   text
          Indicates text that may be selected. Often rendered as an
          I-beam.

   wait
          Indicates that the program is busy and the user should wait.
          Often rendered as a watch or hourglass.

   progress
          A progress indicator. The program is performing some processing,
          but is different from 'wait' in that the user may still interact
          with the program. Often rendered as a spinning beach ball, or an
          arrow with a watch or hourglass.

   help
          Help is available for the object under the cursor. Often
          rendered as a question mark or a balloon.

   <uri>
          The user agent retrieves the cursor from the resource designated
          by the URI. If the user agent cannot handle the first cursor of
          a list of cursors, it should attempt to handle the second, etc.
          If the user agent cannot handle any user-defined cursor, it must
          use the generic cursor at the end of the list. Intrinsic sizes
          for cursors are calculated as for background images, except that
          a UA-defined rectangle is used in place of the rectangle that
          establishes the coordinate system for the 'background-image'
          property. This UA-defined rectangle should be based on the size
          of a typical cursor on the UA's operating system. If the
          resulting cursor size does not fit within this rectangle, the UA
          may proportionally scale the resulting cursor down until it fits
          within the rectangle.

   Example(s):
:link,:visited { cursor: url(example.svg#linkcursor), url(hyper.cur), pointer }

   This example sets the cursor on all hyperlinks (whether visited or not)
   to an external SVG cursor. User agents that do not support SVG cursors
   would simply skip to the next value and attempt to use the "hyper.cur"
   cursor. If that cursor format was also not supported, the UA would skip
   to the next value and simply render the 'pointer' cursor.

18.2 System Colors

   Note. The System Colors are deprecated in the CSS3 Color Module
   [CSS3COLOR].

   In addition to being able to assign pre-defined color values to text,
   backgrounds, etc., CSS2 introduced a set of named color values that
   allows authors to specify colors in a manner that integrates them into
   the operating system's graphic environment.

   For systems that do not have a corresponding value, the specified value
   should be mapped to the nearest system value, or to a default color.

   The following lists additional values for color-related CSS properties
   and their general meaning. Any color property (e.g., 'color' or
   'background-color') can take one of the following names. Although these
   are case-insensitive, it is recommended that the mixed capitalization
   shown below be used, to make the names more legible.

   ActiveBorder
          Active window border.

   ActiveCaption
          Active window caption.

   AppWorkspace
          Background color of multiple document interface.

   Background
          Desktop background.

   ButtonFace
          Face color for three-dimensional display elements.

   ButtonHighlight
          Highlight color for three-dimensional display elements (for
          edges facing away from the light source).

   ButtonShadow
          Shadow color for three-dimensional display elements.

   ButtonText
          Text on push buttons.

   CaptionText
          Text in caption, size box, and scrollbar arrow box.

   GrayText
          Grayed (disabled) text. This color is set to #000 if the current
          display driver does not support a solid gray color.

   Highlight
          Item(s) selected in a control.

   HighlightText
          Text of item(s) selected in a control.

   InactiveBorder
          Inactive window border.

   InactiveCaption
          Inactive window caption.

   InactiveCaptionText
          Color of text in an inactive caption.

   InfoBackground
          Background color for tooltip controls.

   InfoText
          Text color for tooltip controls.

   Menu
          Menu background.

   MenuText
          Text in menus.

   Scrollbar
          Scroll bar gray area.

   ThreeDDarkShadow
          Dark shadow for three-dimensional display elements.

   ThreeDFace
          Face color for three-dimensional display elements.

   ThreeDHighlight
          Highlight color for three-dimensional display elements.

   ThreeDLightShadow
          Light color for three-dimensional display elements (for edges
          facing the light source).

   ThreeDShadow
          Dark shadow for three-dimensional display elements.

   Window
          Window background.

   WindowFrame
          Window frame.

   WindowText
          Text in windows.

   Example(s):

   For example, to set the foreground and background colors of a paragraph
   to the same foreground and background colors of the user's window,
   write the following:
p { color: WindowText; background-color: Window }

18.3 User preferences for fonts

   As for colors, authors may specify fonts in a way that makes use of a
   user's system resources. Please consult the 'font' property for
   details.

18.4 Dynamic outlines: the 'outline' property

   At times, style sheet authors may want to create outlines around visual
   objects such as buttons, active form fields, image maps, etc., to make
   them stand out. CSS 2.1 outlines differ from borders in the following
   ways:
    1. Outlines do not take up space.
    2. Outlines may be non-rectangular.

   The outline properties control the style of these dynamic outlines.

   'outline'

 Value:            [ <'outline-color'> || <'outline-style'> || <'outline-width'>
                   ] | inherit
 Initial:          see individual properties
 Applies to:       all elements
 Inherited:        no
 Percentages:      N/A
 Media:            visual, interactive
 Computed value:   see individual properties

   'outline-width'

          Value:            <border-width> | inherit
          Initial:          medium
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual, interactive
          Computed value:   absolute length; '0' if the outline style is 'none'

   'outline-style'

          Value:            <border-style> | inherit
          Initial:          none
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual, interactive
          Computed value:   as specified

   'outline-color'

          Value:            <color> | invert | inherit
          Initial:          invert
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            visual, interactive
          Computed value:   as specified

   The outline created with the outline properties is drawn "over" a box,
   i.e., the outline is always on top, and does not influence the position
   or size of the box, or of any other boxes. Therefore, displaying or
   suppressing outlines does not cause reflow or overflow.

   The outline may be drawn starting just outside the border edge.

   Outlines may be non-rectangular. For example, if the element is broken
   across several lines, the outline is the minimum outline that encloses
   all the element's boxes. In contrast to borders, the outline is not
   open at the line box's end or start, but is always fully connected if
   possible.

   The 'outline-width' property accepts the same values as 'border-width'.

   The 'outline-style' property accepts the same values as 'border-style',
   except that 'hidden' is not a legal outline style.

   The 'outline-color' accepts all colors, as well as the keyword
   'invert'. 'Invert' is expected to perform a color inversion on the
   pixels on the screen. This is a common trick to ensure the focus border
   is visible, regardless of color background.

   Conformant UAs may ignore the 'invert' value on platforms that do not
   support color inversion of the pixels on the screen. If the UA does not
   support the 'invert' value then the initial value of the
   'outline-color' property is the value of the 'color' property, similar
   to the initial value of the 'border-top-color' property.

   The 'outline' property is a shorthand property, and sets all three of
   'outline-style', 'outline-width', and 'outline-color'.

   Note. The outline is the same on all sides. In contrast to borders,
   there is no 'outline-top' or 'outline-left' property.

   This specification does not define how multiple overlapping outlines
   are drawn, or how outlines are drawn for boxes that are partially
   obscured behind other elements.

   Note. Since the outline does not affect formatting (i.e., no space is
   left for it in the box model), it may well overlap other elements on
   the page.

   Example(s):

   Here's an example of drawing a thick outline around a BUTTON element:
button { outline : thick solid}

   Scripts may be used to dynamically change the width of the outline,
   without provoking a reflow.

  18.4.1 Outlines and the focus

   Graphical user interfaces may use outlines around elements to tell the
   user which element on the page has the focus. These outlines are in
   addition to any borders, and switching outlines on and off should not
   cause the document to reflow. The focus is the subject of user
   interaction in a document (e.g., for entering text, selecting a button,
   etc.). User agents supporting the interactive media group must keep
   track of where the focus lies and must also represent the focus. This
   may be done by using dynamic outlines in conjunction with the :focus
   pseudo-class.

   Example(s):

   For example, to draw a thick black line around an element when it has
   the focus, and a thick red line when it is active, the following rules
   can be used:
:focus  { outline: thick solid black }
:active { outline: thick solid red }

18.5 Magnification

   The CSS working group considers that the magnification of a document or
   portions of a document should not be specified through style sheets.
   User agents may support such magnification in different ways (e.g.,
   larger images, louder sounds, etc.)

   When magnifying a page, UAs should preserve the relationships between
   positioned elements. For example, a comic strip may be composed of
   images with overlaid text elements. When magnifying this page, a user
   agent should keep the text within the comic strip balloon.

                         Appendix A. Aural style sheets

   Contents
     * A.1 The media types 'aural' and 'speech'
     * A.2 Introduction to aural style sheets
          + A.2.1 Angles
          + A.2.2 Times
          + A.2.3 Frequencies
     * A.3 Volume properties: 'volume'
     * A.4 Speaking properties: 'speak'
     * A.5 Pause properties: 'pause-before', 'pause-after', and 'pause'
     * A.6 Cue properties: 'cue-before', 'cue-after', and 'cue'
     * A.7 Mixing properties: 'play-during'
     * A.8 Spatial properties: 'azimuth' and 'elevation'
     * A.9 Voice characteristic properties: 'speech-rate', 'voice-family',
       'pitch', 'pitch-range', 'stress', and 'richness'
     * A.10 Speech properties: 'speak-punctuation' and 'speak-numeral'
     * A.11 Audio rendering of tables
          + A.11.1 Speaking headers: the 'speak-header' property
     * A.12 Sample style sheet for HTML
     * A.13 Emacspeak

   This chapter is informative. UAs are not required to implement the
   properties of this chapter in order to conform to CSS 2.1.

A.1 The media types 'aural' and 'speech'

   We expect that in a future level of CSS there will be new properties
   and values defined for speech output. Therefore CSS 2.1 reserves the
   'speech' media type (see chapter 7, "Media types"), but does not yet
   define which properties do or do not apply to it.

   The properties in this appendix apply to a media type 'aural', that was
   introduced in CSS2. The type 'aural' is now deprecated.

   This means that a style sheet such as
@media speech {
  body { voice-family: Paul }
}

   is valid, but that its meaning is not defined by CSS 2.1, while
@media aural {
  body { voice-family: Paul }
}

   is deprecated, but defined by this appendix.

A.2 Introduction to aural style sheets

   The aural rendering of a document, already commonly used by the blind
   and print-impaired communities, combines speech synthesis and "auditory
   icons." Often such aural presentation occurs by converting the document
   to plain text and feeding this to a screen reader -- software or
   hardware that simply reads all the characters on the screen. This
   results in less effective presentation than would be the case if the
   document structure were retained. Style sheet properties for aural
   presentation may be used together with visual properties (mixed media)
   or as an aural alternative to visual presentation.

   Besides the obvious accessibility advantages, there are other large
   markets for listening to information, including in-car use, industrial
   and medical documentation systems (intranets), home entertainment, and
   to help users learning to read or who have difficulty reading.

   When using aural properties, the canvas consists of a three-dimensional
   physical space (sound surrounds) and a temporal space (one may specify
   sounds before, during, and after other sounds). The CSS properties also
   allow authors to vary the quality of synthesized speech (voice type,
   frequency, inflection, etc.).

   Example(s):

h1, h2, h3, h4, h5, h6 {
    voice-family: paul;
    stress: 20;
    richness: 90;
    cue-before: url("ping.au")
}
p.heidi { azimuth: center-left }
p.peter { azimuth: right }
p.goat  { volume: x-soft }

   This will direct the speech synthesizer to speak headers in a voice (a
   kind of "audio font") called "paul", on a flat tone, but in a very rich
   voice. Before speaking the headers, a sound sample will be played from
   the given URL. Paragraphs with class "heidi" will appear to come from
   front left (if the sound system is capable of spatial audio), and
   paragraphs of class "peter" from the right. Paragraphs with class
   "goat" will be very soft.

  A.2.1 Angles

   Angle values are denoted by <angle> in the text. Their format is a
   <number> immediately followed by an angle unit identifier.

   Angle unit identifiers are:
     * deg: degrees
     * grad: grads
     * rad: radians

   Angle values may be negative. They should be normalized to the range
   0-360deg by the user agent. For example, -10deg and 350deg are
   equivalent.

   For example, a right angle is '90deg' or '100grad' or
   '1.570796326794897rad'.

   Like for <length>, the unit may be omitted, if the value is zero:
   '0deg' may be written as '0'.

  A.2.2 Times

   Time values are denoted by <time> in the text. Their format is a
   <number> immediately followed by a time unit identifier.

   Time unit identifiers are:
     * ms: milliseconds
     * s: seconds

   Time values may not be negative.

   Like for <length>, the unit may be omitted, if the value is zero: '0s'
   may be written as '0'.

  A.2.3 Frequencies

   Frequency values are denoted by <frequency> in the text. Their format
   is a <number> immediately followed by a frequency unit identifier.

   Frequency unit identifiers are:
     * Hz: Hertz
     * kHz: kilohertz

   Frequency values may not be negative.

   For example, 200Hz (or 200hz) is a bass sound, and 6kHz is a treble
   sound.

   Like for <length>, the unit may be omitted, if the value is zero: '0Hz'
   may be written as '0'.

A.3 Volume properties: 'volume'

   'volume'

   Value:            <number> | <percentage> | silent | x-soft | soft | medium |
                     loud | x-loud | inherit
   Initial:          medium
   Applies to:       all elements
   Inherited:        yes
   Percentages:      refer to inherited value
   Media:            aural
   Computed value:   number

   Volume refers to the median volume of the waveform. In other words, a
   highly inflected voice at a volume of 50 might peak well above that.
   The overall values are likely to be human adjustable for comfort, for
   example with a physical volume control (which would increase both the 0
   and 100 values proportionately); what this property does is adjust the
   dynamic range.

   Values have the following meanings:

   <number>
          Any number between '0' and '100'. '0' represents the minimum
          audible volume level and 100 corresponds to the maximum
          comfortable level.

   <percentage>
          Percentage values are calculated relative to the inherited
          value, and are then clipped to the range '0' to '100'.

   silent
          No sound at all. The value '0' does not mean the same as
          'silent'.

   x-soft
          Same as '0'.

   soft
          Same as '25'.

   medium
          Same as '50'.

   loud
          Same as '75'.

   x-loud
          Same as '100'.

   User agents should allow the values corresponding to '0' and '100' to
   be set by the listener. No one setting is universally applicable;
   suitable values depend on the equipment in use (speakers, headphones),
   the environment (in car, home theater, library) and personal
   preferences. Some examples:
     * A browser for in-car use has a setting for when there is lots of
       background noise. '0' would map to a fairly high level and '100' to
       a quite high level. The speech is easily audible over the road
       noise but the overall dynamic range is compressed. Cars with better
       insulation might allow a wider dynamic range.
     * Another speech browser is being used in an apartment, late at
       night, or in a shared study room. '0' is set to a very quiet level
       and '100' to a fairly quiet level, too. As with the first example,
       there is a low slope; the dynamic range is reduced. The actual
       volumes are low here, whereas they were high in the first example.
     * In a quiet and isolated house, an expensive hi-fi home theater
       setup. '0' is set fairly low and '100' to quite high; there is wide
       dynamic range.

   The same author style sheet could be used in all cases, simply by
   mapping the '0' and '100' points suitably at the client side.

A.4 Speaking properties: 'speak'

   'speak'

          Value:            normal | none | spell-out | inherit
          Initial:          normal
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            aural
          Computed value:   as specified

   This property specifies whether text will be rendered aurally and if
   so, in what manner. The possible values are:

   none
          Suppresses aural rendering so that the element requires no time
          to render. Note, however, that descendants may override this
          value and will be spoken. (To be sure to suppress rendering of
          an element and its descendants, use the 'display' property).

   normal
          Uses language-dependent pronunciation rules for rendering an
          element and its children.

   spell-out
          Spells the text one letter at a time (useful for acronyms and
          abbreviations).

   Note the difference between an element whose 'volume' property has a
   value of 'silent' and an element whose 'speak' property has the value
   'none'. The former takes up the same time as if it had been spoken,
   including any pause before and after the element, but no sound is
   generated. The latter requires no time and is not rendered (though its
   descendants may be).

A.5 Pause properties: 'pause-before', 'pause-after', and 'pause'

   'pause-before'

          Value:            <time> | <percentage> | inherit
          Initial:          0
          Applies to:       all elements
          Inherited:        no
          Percentages:      see prose
          Media:            aural
          Computed value:   time

   'pause-after'

          Value:            <time> | <percentage> | inherit
          Initial:          0
          Applies to:       all elements
          Inherited:        no
          Percentages:      see prose
          Media:            aural
          Computed value:   time;;

   These properties specify a pause to be observed before (or after)
   speaking an element's content. Values have the following meanings:

   Note. In CSS3 pauses are inserted around the cues and content rather
   than between them. See [CSS3SPEECH] for details.

   <time>
          Expresses the pause in absolute time units (seconds and
          milliseconds).

   <percentage>
          Refers to the inverse of the value of the 'speech-rate'
          property. For example, if the speech-rate is 120 words per
          minute (i.e., a word takes half a second, or 500ms) then a
          'pause-before' of 100% means a pause of 500 ms and a
          'pause-before' of 20% means 100ms.

   The pause is inserted between the element's content and any
   'cue-before' or 'cue-after' content.

   Authors should use relative units to create more robust style sheets in
   the face of large changes in speech-rate.

   'pause'

          Value:            [ [<time> | <percentage>]{1,2} ] | inherit
          Initial:          see individual properties
          Applies to:       all elements
          Inherited:        no
          Percentages:      see descriptions of 'pause-before' and 'pause-after'
          Media:            aural
          Computed value:   see individual properties

   The 'pause' property is a shorthand for setting 'pause-before' and
   'pause-after'. If two values are given, the first value is
   'pause-before' and the second is 'pause-after'. If only one value is
   given, it applies to both properties.

   Example(s):

h1 { pause: 20ms } /* pause-before: 20ms; pause-after: 20ms */
h2 { pause: 30ms 40ms } /* pause-before: 30ms; pause-after: 40ms */
h3 { pause-after: 10ms } /* pause-before unspecified; pause-after: 10ms */

A.6 Cue properties: 'cue-before', 'cue-after', and 'cue'

   'cue-before'

          Value:            <uri> | none | inherit
          Initial:          none
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            aural
          Computed value:   absolute URI or 'none'

   'cue-after'

          Value:            <uri> | none | inherit
          Initial:          none
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            aural
          Computed value:   absolute URI or 'none'

   Auditory icons are another way to distinguish semantic elements. Sounds
   may be played before and/or after the element to delimit it. Values
   have the following meanings:

   <uri>
          The URI must designate an auditory icon resource. If the URI
          resolves to something other than an audio file, such as an
          image, the resource should be ignored and the property treated
          as if it had the value 'none'.

   none
          No auditory icon is specified.

   Example(s):

a {cue-before: url("bell.aiff"); cue-after: url("dong.wav") }
h1 {cue-before: url("pop.au"); cue-after: url("pop.au") }

   'cue'

          Value:            [ <'cue-before'> || <'cue-after'> ] | inherit
          Initial:          see individual properties
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            aural
          Computed value:   see individual properties

   The 'cue' property is a shorthand for setting 'cue-before' and
   'cue-after'. If two values are given, the first value is 'cue-before'
   and the second is 'cue-after'. If only one value is given, it applies
   to both properties.

   Example(s):

   The following two rules are equivalent:
h1 {cue-before: url("pop.au"); cue-after: url("pop.au") }
h1 {cue: url("pop.au") }

   If a user agent cannot render an auditory icon (e.g., the user's
   environment does not permit it), we recommend that it produce an
   alternative cue.

   Please see the sections on the :before and :after pseudo-elements for
   information on other content generation techniques. 'Cue-before' sounds
   and 'pause-before' gaps are inserted before content from the ':before'
   pseudo-element. Similarly, 'pause-after' gaps and 'cue-after' sounds
   are inserted after content from the ':after' pseudo-element.

A.7 Mixing properties: 'play-during'

   'play-during'

          Value:            <uri> [ mix || repeat ]? | auto | none | inherit
          Initial:          auto
          Applies to:       all elements
          Inherited:        no
          Percentages:      N/A
          Media:            aural
          Computed value:   absolute URI, rest as specified

   Similar to the 'cue-before' and 'cue-after' properties, this property
   specifies a sound to be played as a background while an element's
   content is spoken. Values have the following meanings:

   <uri>
          The sound designated by this <uri> is played as a background
          while the element's content is spoken.

   mix
          When present, this keyword means that the sound inherited from
          the parent element's 'play-during' property continues to play
          and the sound designated by the <uri> is mixed with it. If 'mix'
          is not specified, the element's background sound replaces the
          parent's.

   repeat
          When present, this keyword means that the sound will repeat if
          it is too short to fill the entire duration of the element.
          Otherwise, the sound plays once and then stops. This is similar
          to the 'background-repeat' property. If the sound is too long
          for the element, it is clipped once the element has been spoken.

   auto
          The sound of the parent element continues to play (it is not
          restarted, which would have been the case if this property had
          been inherited).

   none
          This keyword means that there is silence. The sound of the
          parent element (if any) is silent during the current element and
          continues after the current element.

   Example(s):

blockquote.sad { play-during: url("violins.aiff") }
blockquote Q   { play-during: url("harp.wav") mix }
span.quiet     { play-during: none }

A.8 Spatial properties: 'azimuth' and 'elevation'

   Spatial audio is an important stylistic property for aural
   presentation. It provides a natural way to tell several voices apart,
   as in real life (people rarely all stand in the same spot in a room).
   Stereo speakers produce a lateral sound stage. Binaural headphones or
   the increasingly popular 5-speaker home theater setups can generate
   full surround sound, and multi-speaker setups can create a true
   three-dimensional sound stage. VRML 2.0 also includes spatial audio,
   which implies that in time consumer-priced spatial audio hardware will
   become more widely available.

   'azimuth'

   Value:   <angle> | [[ left-side | far-left | left | center-left |
   center | center-right | right | far-right | right-side ] || behind ] |
   leftwards | rightwards | inherit
   Initial:   center
   Applies to:   all elements
   Inherited:   yes
   Percentages:   N/A
   Media:   aural
   Computed value:   normalized angle

   Values have the following meanings:

   <angle>
          Position is described in terms of an angle within the range
          '-360deg' to '360deg'. The value '0deg' means directly ahead in
          the center of the sound stage. '90deg' is to the right, '180deg'
          behind, and '270deg' (or, equivalently and more conveniently,
          '-90deg') to the left.

   left-side
          Same as '270deg'. With 'behind', '270deg'.

   far-left
          Same as '300deg'. With 'behind', '240deg'.

   left
          Same as '320deg'. With 'behind', '220deg'.

   center-left
          Same as '340deg'. With 'behind', '200deg'.

   center
          Same as '0deg'. With 'behind', '180deg'.

   center-right
          Same as '20deg'. With 'behind', '160deg'.

   right
          Same as '40deg'. With 'behind', '140deg'.

   far-right
          Same as '60deg'. With 'behind', '120deg'.

   right-side
          Same as '90deg'. With 'behind', '90deg'.

   leftwards
          Moves the sound to the left, relative to the current angle. More
          precisely, subtracts 20 degrees. Arithmetic is carried out
          modulo 360 degrees. Note that 'leftwards' is more accurately
          described as "turned counter-clockwise," since it always
          subtracts 20 degrees, even if the inherited azimuth is already
          behind the listener (in which case the sound actually appears to
          move to the right).

   rightwards
          Moves the sound to the right, relative to the current angle.
          More precisely, adds 20 degrees. See 'leftwards' for arithmetic.

   This property is most likely to be implemented by mixing the same
   signal into different channels at differing volumes. It might also use
   phase shifting, digital delay, and other such techniques to provide the
   illusion of a sound stage. The precise means used to achieve this
   effect and the number of speakers used to do so are user
   agent-dependent; this property merely identifies the desired end
   result.

   Example(s):

h1   { azimuth: 30deg }
td.a { azimuth: far-right }          /*  60deg */
#12  { azimuth: behind far-right }   /* 120deg */
p.comment { azimuth: behind }        /* 180deg */

   If spatial-azimuth is specified and the output device cannot produce
   sounds behind the listening position, user agents should convert values
   in the rearwards hemisphere to forwards hemisphere values. One method
   is as follows:
     * if 90deg < x <= 180deg then x := 180deg - x
     * if 180deg < x <= 270deg then x := 540deg - x

   'elevation'

    Value:            <angle> | below | level | above | higher | lower | inherit
    Initial:          level
    Applies to:       all elements
    Inherited:        yes
    Percentages:      N/A
    Media:            aural
    Computed value:   normalized angle

   Values of this property have the following meanings:

   <angle>
          Specifies the elevation as an angle, between '-90deg' and
          '90deg'. '0deg' means on the forward horizon, which loosely
          means level with the listener. '90deg' means directly overhead
          and '-90deg' means directly below.

   below
          Same as '-90deg'.

   level
          Same as '0deg'.

   above
          Same as '90deg'.

   higher
          Adds 10 degrees to the current elevation.

   lower
          Subtracts 10 degrees from the current elevation.

   The precise means used to achieve this effect and the number of
   speakers used to do so are undefined. This property merely identifies
   the desired end result.

   Example(s):

h1   { elevation: above }
tr.a { elevation: 60deg }
tr.b { elevation: 30deg }
tr.c { elevation: level }

A.9 Voice characteristic properties: 'speech-rate', 'voice-family', 'pitch',
'pitch-range', 'stress', and 'richness'

   'speech-rate'

  Value:            <number> | x-slow | slow | medium | fast | x-fast | faster |
                    slower | inherit
  Initial:          medium
  Applies to:       all elements
  Inherited:        yes
  Percentages:      N/A
  Media:            aural
  Computed value:   number

   This property specifies the speaking rate. Note that both absolute and
   relative keyword values are allowed (compare with 'font-size'). Values
   have the following meanings:

   <number>
          Specifies the speaking rate in words per minute, a quantity that
          varies somewhat by language but is nevertheless widely supported
          by speech synthesizers.

   x-slow
          Same as 80 words per minute.

   slow
          Same as 120 words per minute

   medium
          Same as 180 - 200 words per minute.

   fast
          Same as 300 words per minute.

   x-fast
          Same as 500 words per minute.

   faster
          Adds 40 words per minute to the current speech rate.

   slower
          Subtracts 40 words per minutes from the current speech rate.

   'voice-family'

 Value:            [[<specific-voice> | <generic-voice> ],]* [<specific-voice> |
                   <generic-voice> ] | inherit
 Initial:          depends on user agent
 Applies to:       all elements
 Inherited:        yes
 Percentages:      N/A
 Media:            aural
 Computed value:   as specified

   The value is a comma-separated, prioritized list of voice family names
   (compare with 'font-family'). Values have the following meanings:

   <generic-voice>
          Values are voice families. Possible values are 'male', 'female',
          and 'child'.

   <specific-voice>
          Values are specific instances (e.g., comedian, trinoids, carlos,
          lani).

   Example(s):

h1 { voice-family: announcer, male }
p.part.romeo  { voice-family: romeo, male }
p.part.juliet { voice-family: juliet, female }

   Names of specific voices may be quoted, and indeed must be quoted if
   any of the words that make up the name does not conform to the syntax
   rules for identifiers. It is also recommended to quote specific voices
   with a name consisting of more than one word. If quoting is omitted,
   any white space characters before and after the voice family name are
   ignored and any sequence of white space characters inside the voice
   family name is converted to a single space.

   'pitch'

  Value:            <frequency> | x-low | low | medium | high | x-high | inherit
  Initial:          medium
  Applies to:       all elements
  Inherited:        yes
  Percentages:      N/A
  Media:            aural
  Computed value:   frequency

   Specifies the average pitch (a frequency) of the speaking voice. The
   average pitch of a voice depends on the voice family. For example, the
   average pitch for a standard male voice is around 120Hz, but for a
   female voice, it's around 210Hz.

   Values have the following meanings:

   <frequency>
          Specifies the average pitch of the speaking voice in hertz (Hz).

   x-low, low, medium, high, x-high
          These values do not map to absolute frequencies since these
          values depend on the voice family. User agents should map these
          values to appropriate frequencies based on the voice family and
          user environment. However, user agents must map these values in
          order (i.e., 'x-low' is a lower frequency than 'low', etc.).

   'pitch-range'

          Value:            <number> | inherit
          Initial:          50
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            aural
          Computed value:   as specified

   Specifies variation in average pitch. The perceived pitch of a human
   voice is determined by the fundamental frequency and typically has a
   value of 120Hz for a male voice and 210Hz for a female voice. Human
   languages are spoken with varying inflection and pitch; these
   variations convey additional meaning and emphasis. Thus, a highly
   animated voice, i.e., one that is heavily inflected, displays a high
   pitch range. This property specifies the range over which these
   variations occur, i.e., how much the fundamental frequency may deviate
   from the average pitch.

   Values have the following meanings:

   <number>
          A value between '0' and '100'. A pitch range of '0' produces a
          flat, monotonic voice. A pitch range of 50 produces normal
          inflection. Pitch ranges greater than 50 produce animated
          voices.

   'stress'

          Value:            <number> | inherit
          Initial:          50
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            aural
          Computed value:   as specified

   Specifies the height of "local peaks" in the intonation contour of a
   voice. For example, English is a stressed language, and different parts
   of a sentence are assigned primary, secondary, or tertiary stress. The
   value of 'stress' controls the amount of inflection that results from
   these stress markers. This property is a companion to the 'pitch-range'
   property and is provided to allow developers to exploit higher-end
   auditory displays.

   Values have the following meanings:

   <number>
          A value, between '0' and '100'. The meaning of values depends on
          the language being spoken. For example, a level of '50' for a
          standard, English-speaking male voice (average pitch = 122Hz),
          speaking with normal intonation and emphasis would have a
          different meaning than '50' for an Italian voice.

   'richness'

          Value:            <number> | inherit
          Initial:          50
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            aural
          Computed value:   as specified

   Specifies the richness, or brightness, of the speaking voice. A rich
   voice will "carry" in a large room, a smooth voice will not. (The term
   "smooth" refers to how the wave form looks when drawn.)

   Values have the following meanings:

   <number>
          A value between '0' and '100'. The higher the value, the more
          the voice will carry. A lower value will produce a soft,
          mellifluous voice.

A.10 Speech properties: 'speak-punctuation' and 'speak-numeral'

   An additional speech property, 'speak-header', is described below.

   'speak-punctuation'

          Value:            code | none | inherit
          Initial:          none
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            aural
          Computed value:   as specified

   This property specifies how punctuation is spoken. Values have the
   following meanings:

   code
          Punctuation such as semicolons, braces, and so on are to be
          spoken literally.

   none
          Punctuation is not to be spoken, but instead rendered naturally
          as various pauses.

   'speak-numeral'

          Value:            digits | continuous | inherit
          Initial:          continuous
          Applies to:       all elements
          Inherited:        yes
          Percentages:      N/A
          Media:            aural
          Computed value:   as specified

   This property controls how numerals are spoken. Values have the
   following meanings:

   digits
          Speak the numeral as individual digits. Thus, "237" is spoken
          "Two Three Seven".

   continuous
          Speak the numeral as a full number. Thus, "237" is spoken "Two
          hundred thirty seven". Word representations are
          language-dependent.

A.11 Audio rendering of tables

   When a table is spoken by a speech generator, the relation between the
   data cells and the header cells must be expressed in a different way
   than by horizontal and vertical alignment. Some speech browsers may
   allow a user to move around in the 2-dimensional space, thus giving
   them the opportunity to map out the spatially represented relations.
   When that is not possible, the style sheet must specify at which points
   the headers are spoken.

  A.11.1 Speaking headers: the 'speak-header' property

   'speak-header'

          Value:            once | always | inherit
          Initial:          once
          Applies to:       elements that have table header information
          Inherited:        yes
          Percentages:      N/A
          Media:            aural
          Computed value:   as specified

   This property specifies whether table headers are spoken before every
   cell, or only before a cell when that cell is associated with a
   different header than the previous cell. Values have the following
   meanings:

   once
          The header is spoken one time, before a series of cells.

   always
          The header is spoken before every pertinent cell.

   Each document language may have different mechanisms that allow authors
   to specify headers. For example, in HTML 4 ([HTML4]), it is possible to
   specify header information with three different attributes ("headers",
   "scope", and "axis"), and the specification gives an algorithm for
   determining header information when these attributes have not been
   specified.

   Image of a table created in MS Word    [D]

   Image of a table with header cells ("San Jose" and "Seattle") that are
   not in the same column or row as the data they apply to.

   This HTML example presents the money spent on meals, hotels and
   transport in two locations (San Jose and Seattle) for successive days.
   Conceptually, you can think of the table in terms of an n-dimensional
   space. The headers of this space are: location, day, category and
   subtotal. Some cells define marks along an axis while others give money
   spent at points within this space. The markup for this table is:
<TABLE>
<CAPTION>Travel Expense Report</CAPTION>
<TR>
  <TH></TH>
  <TH>Meals</TH>
  <TH>Hotels</TH>
  <TH>Transport</TH>
  <TH>subtotal</TH>
</TR>
<TR>
  <TH id="san-jose" axis="san-jose">San Jose</TH>
</TR>
<TR>
  <TH headers="san-jose">25-Aug-97</TH>
  <TD>37.74</TD>
  <TD>112.00</TD>
  <TD>45.00</TD>
  <TD></TD>
</TR>
<TR>
  <TH headers="san-jose">26-Aug-97</TH>
  <TD>27.28</TD>
  <TD>112.00</TD>
  <TD>45.00</TD>
  <TD></TD>
</TR>
<TR>
  <TH headers="san-jose">subtotal</TH>
  <TD>65.02</TD>
  <TD>224.00</TD>
  <TD>90.00</TD>
  <TD>379.02</TD>
</TR>
<TR>
  <TH id="seattle" axis="seattle">Seattle</TH>
</TR>
<TR>
  <TH headers="seattle">27-Aug-97</TH>
  <TD>96.25</TD>
  <TD>109.00</TD>
  <TD>36.00</TD>
  <TD></TD>
</TR>
<TR>
  <TH headers="seattle">28-Aug-97</TH>
  <TD>35.00</TD>
  <TD>109.00</TD>
  <TD>36.00</TD>
  <TD></TD>
</TR>
<TR>
  <TH headers="seattle">subtotal</TH>
  <TD>131.25</TD>
  <TD>218.00</TD>
  <TD>72.00</TD>
  <TD>421.25</TD>
</TR>
<TR>
  <TH>Totals</TH>
  <TD>196.27</TD>
  <TD>442.00</TD>
  <TD>162.00</TD>
  <TD>800.27</TD>
</TR>
</TABLE>

   By providing the data model in this way, authors make it possible for
   speech enabled-browsers to explore the table in rich ways, e.g., each
   cell could be spoken as a list, repeating the applicable headers before
   each data cell:
  San Jose, 25-Aug-97, Meals:  37.74
  San Jose, 25-Aug-97, Hotels:  112.00
  San Jose, 25-Aug-97, Transport:  45.00
 ...

   The browser could also speak the headers only when they change:
San Jose, 25-Aug-97, Meals: 37.74
    Hotels: 112.00
    Transport: 45.00
  26-Aug-97, Meals: 27.28
    Hotels: 112.00
...

A.12 Sample style sheet for HTML

   This style sheet describes a possible rendering of HTML 4:
@media aural {
h1, h2, h3,
h4, h5, h6    { voice-family: paul, male; stress: 20; richness: 90 }
h1            { pitch: x-low; pitch-range: 90 }
h2            { pitch: x-low; pitch-range: 80 }
h3            { pitch: low; pitch-range: 70 }
h4            { pitch: medium; pitch-range: 60 }
h5            { pitch: medium; pitch-range: 50 }
h6            { pitch: medium; pitch-range: 40 }
li, dt, dd    { pitch: medium; richness: 60 }
dt            { stress: 80 }
pre, code, tt { pitch: medium; pitch-range: 0; stress: 0; richness: 80 }
em            { pitch: medium; pitch-range: 60; stress: 60; richness: 50 }
strong        { pitch: medium; pitch-range: 60; stress: 90; richness: 90 }
dfn           { pitch: high; pitch-range: 60; stress: 60 }
s, strike     { richness: 0 }
i             { pitch: medium; pitch-range: 60; stress: 60; richness: 50 }
b             { pitch: medium; pitch-range: 60; stress: 90; richness: 90 }
u             { richness: 0 }
a:link        { voice-family: harry, male }
a:visited     { voice-family: betty, female }
a:active      { voice-family: betty, female; pitch-range: 80; pitch: x-high }
}

A.13 Emacspeak

   For information, here is the list of properties implemented by
   Emacspeak, a speech subsystem for the Emacs editor.
     * voice-family
     * stress (but with a different range of values)
     * richness (but with a different range of values)
     * pitch (but with differently named values)
     * pitch-range (but with a different range of values)

   (We thank T. V. Raman for the information about implementation status
   of aural properties.)

                            Appendix B. Bibliography

   Contents
     * B.1 Normative references
     * B.2 Informative references

B.1 Normative references

   [COLORIMETRY]
          "Colorimetry", Third Edition, Commission Internationale de
          l'Eclairage, CIE Publication 15:2004, ISBN 3-901-906-33-9.
          Available at http://www.cie.co.at/publ/abst/15-2004.html

   [FLEX]
          "Flex: The Lexical Scanner Generator", Version 2.3.7, ISBN
          1882114213.

   [HTML4]
          "HTML 4.01 Specification", D. Raggett, A. Le Hors, I. Jacobs, 24
          December 1999.
          The latest version of the specification is available at
          http://www.w3.org/TR/html4/. The Recommendation defines three
          document type definitions: Strict, Transitional, and Frameset,
          all reachable from the Recommendation.

   [ICC42]
          Specification ICC.1:2004-10 (Profile version 4.2.0.0) Image
          technology colour management – Architecture, profile format, and
          data structure.
          Available at http://www.color.org/icc_specs2.html

   [ISO8879]
          "ISO 8879:1986(E): Information processing - Text and Office
          Systems - Standard Generalized Markup Language (SGML)",
          International Organization for Standardization (ISO), 15 October
          1986.

   [ISO10646]
          "Information Technology - Universal Multiple- Octet Coded
          Character Set (UCS) - Part 1: Architecture and Basic
          Multilingual Plane", ISO/IEC 10646-1:2003. Useful roadmap of the
          BMP and plane 1 documents show which scripts sit at which
          numeric ranges.

   [PNG]
          "Portable Network Graphics (PNG) Specification (Second
          Edition)", David Duce, ed., 10 November 2003.
          Available at http://www.w3.org/TR/PNG/.

   [RFC3986]
          "Uniform Resource Identifier (URI): Generic Syntax," T.
          Berners-Lee, R. Fielding, L. Masinter, January 2005.
          Available at http://www.ietf.org/rfc/rfc3986.

   [RFC2045]
          "Multipurpose Internet Mail Extensions (MIME) Part One: Format
          of Internet Message Bodies", N. Freed and N. Borenstein,
          November 1996.
          Available at http://www.ietf.org/rfc/rfc2045.txt. Note that this
          RFC obsoletes RFC1521, RFC1522, and RFC1590.

   [RFC2616]
          "HTTP Version 1.1 ", R. Fielding, J. Gettys, J. Mogul, et al.,
          June 1999.
          Available at http://www.ietf.org/rfc/rfc2616.txt.

   [RFC2119]
          "Key words for use in RFCs to Indicate Requirement Levels", S.
          Bradner, March 1997.
          Available at http://www.ietf.org/rfc/rfc2119.txt.

   [RFC2318]
          "The text/css Media Type", H. Lie, B. Bos, C. Lilley, March
          1998.
          Available at http://www.ietf.org/rfc/rfc2318.txt.

   [SRGB]
          IEC 61966-2-1 (1999-10) - "Multimedia systems and equipment -
          Colour measurement and management - Part 2-1: Colour management
          - Default RGB colour space - sRGB, ISBN: 2-8318-4989-6 - ICS
          codes: 33.160.60, 37.080 - TC 100 - 51 pp.
          Available at
          http://domino.iec.ch/webstore/webstore.nsf/artnum/025408

   [UAAG10]
          "User Agent Accessibility Guidelines 1.0." Ian Jacobs, Jon
          Gunderson, Eric Hansen (editors). 17 December 2002.
          Available at http://www.w3.org/TR/2002/REC-UAAG10-20021217

   [UAX9]
          "Unicode Bidirectional Algorithm", Mark Davis. (Unicode Standard
          Annex #9.) 27 September 2010.
          Available at http://www.unicode.org/reports/tr9/

   [UNICODE]
          The Unicode Consortium. The Unicode Standard, Version 6.0.0,
          (Mountain View, CA: The Unicode Consortium, 2011. ISBN
          978-1-936213-01-6) and as updated from time to time by the
          publication of new versions. (See
          http://www.unicode.org/unicode/standard/versions/ for the latest
          version and additional information on versions of the standard
          and of the Unicode Character Database).
          Available at http://www.unicode.org/versions/Unicode6.0.0/

   [XML10]
          "Extensible Markup Language (XML) 1.0 (fifth edition)" T. Bray,
          J. Paoli, C.M. Sperberg-McQueen, Eve Maler, François Yergeau,
          editors, 26 November 2008.
          Available at http://www.w3.org/TR/REC-xml/.

   [YACC]
          "YACC - Yet another compiler compiler", S. C. Johnson, Technical
          Report, Murray Hill, 1975.

B.2 Informative references

   [CHARSETS]
          Registered charset values. Download a list of registered charset
          values from http://www.iana.org/assignments/character-sets.

   [CSS1]
          "Cascading Style Sheets, level 1", H. W. Lie and B. Bos, 17
          December 1996, revised 11 January 1999
          The latest version is available at http://www.w3.org/TR/CSS1

   [CSS2]
          "Cascading Style Sheets, level 2, CSS2 Specification", B. Bos,
          H. W. Lie, C. Lilley and I. Jacobs, 12 May 1998 (revised 11
          April 2008),
          http://www.w3.org/TR/2008/REC-CSS2-20080411/

   [CSS3COLOR]
          "CSS3 Color Module," Tantek Çelik, Chris Lilley, 28 October
          2010, W3C Proposed Recommendation. Available at
          http://www.w3.org/TR/2010/PR-css3-color-20101028/

   [CSS3LIST]
          "CSS3 module: lists," Tantek Çelik, Ian Hickson, 7 November
          2002, W3C working draft (work in progress). Available at
          http://www.w3.org/TR/2002/WD-css3-lists-20021107

   [CSS3SEL]
          "Selectors", D. Glazman, T. Çelik, I. Hickson, 15 December 2009
          Available at
          http://www.w3.org/TR/2009/PR-css3-selectors-20091215/

   [CSS3SPEECH]
          "CSS3 Speech Module", David Raggett, Daniel Glazman, Claudio
          Santambrogio, Daniel Weck, 19 April 2011, W3C Working Draft
          (work in progress). Available at
          http://www.w3.org/TR/2011/WD-css3-speech-20110419/

   [DOM-LEVEL-3-CORE]
          "Document Object Model (DOM) Level 3 Core Specification", A. Le
          Hors, P. Le Hégaret, et al. (eds.), 7 April 2004, W3C
          Recommendation. Available at
          http://www.w3.org/TR/2004/REC-DOM-Level-3-Core-20040407/.

   [MATH30]
          "Mathematical Markup Language (MathML) Version 3.0", D.
          Carlisle, P. Ion, R. Miner, 21 October 2010
          Available at http://www.w3.org/TR/2010/REC-MathML3-20101021/

   [MEDIAQ]
          "Media Queries", Håkon Wium Lie, Tantek Çelik, Daniel Glazman,
          Anne van Kesteren, 27 July 2010
          (Work in progress.) Available at
          http://www.w3.org/TR/2010/CR-css3-mediaqueries-20100727/

   [P3P]
          "The Platform for Privacy Preferences 1.0 (P3P1.0)
          Specification", L. Cranor, M. Langheinrich, M. Marchiori, M.
          Presler-Marshall, J. Reagle, 16 April 2002
          Available at http://www.w3.org/TR/2002/REC-P3P-20020416

   [BCP47]
          "Tags for Identifying Languages", A. Phillips, M. Davis,
          September 2009.
          Available at http://www.rfc-editor.org/rfc/bcp/bcp47.txt.

   [SVG11]
          "Scalable Vector Graphics (SVG) 1.1 Specification", J.
          Ferraiolo, et.al. 14 January 2003
          Available at http://www.w3.org/TR/2003/REC-SVG11-20030114

   [WVAG20]
          "Web Content Accessibility Guidelines (WCAG) 2.0", Ben Caldwell,
          Michael Cooper, Loretta Guarino Reid, Gregg Vanderheiden, 11
          December 2008.
          Available at: http://www.w3.org/TR/2008/REC-WCAG20-20081211/.

   [XHTML]
          "XHTML 1.0 The Extensible HyperText Markup Language", various
          authors,
          Available at: http://www.w3.org/TR/xhtml1/.

   [XMLID]
          "xml:id Version 1.0", J. Marsh, D. Veillard N. Walsh, 9
          September 2005, W3C Recommendation. Available at:
          http://www.w3.org/TR/2005/REC-xml-id-20050909/.

   [XMLNAMESPACES]
          "Namespaces in XML 1.0 (third edition)", T. Bray, D. Hollander,
          A. Layman, R. Tobin, H. S. Thompson, 8 December 2009
          Available at: http://www.w3.org/TR/2009/REC-xml-names-20091208/.

                              Appendix C. Changes

   Contents
     * C.1 Additional property values
          + C.1.1 Section 4.3.6 Colors
          + C.1.2 Section 9.2.4 The 'display' property
          + C.1.3 Section 12.2 The 'content' property
          + C.1.4 Section 16.6 White space: the 'white-space' property
          + C.1.5 Section 18.1 Cursors: the 'cursor' property
     * C.2 Changes
          + C.2.1 Section 1.1 CSS 2.1 vs CSS 2
          + C.2.2 Section 1.2 Reading the specification
          + C.2.3 Section 1.3 How the specification is organized
          + C.2.4 Section 1.4.2.1 Value
          + C.2.5 Section 1.4.2.6 Media groups
          + C.2.6 Section 1.4.2.7 Computed value
          + C.2.7 Section 1.4.4 Notes and examples
          + C.2.8 Section 1.5 Acknowledgments
          + C.2.9 Section 3.2 Conformance
          + C.2.10 Section 3.3 Error Conditions
          + C.2.11 Section 4.1.1 Tokenization
          + C.2.12 Section 4.1.3 Characters and case
          + C.2.13 Section 4.2 Rules for handling parsing errors
          + C.2.14 Section 4.3 Values
          + C.2.15 Section 4.3.2 Lengths
          + C.2.16 Section 4.3.4 URLs and URIs
          + C.2.17 Section 4.3.5 Counters
          + C.2.18 Section 4.3.6 Colors
          + C.2.19 Section 4.3.8 Unsupported Values
          + C.2.20 Section 4.4 CSS style sheet representation
          + C.2.21 Section 5.8.1 Matching attributes and attribute values
          + C.2.22 Section 5.8.3 Class selectors
          + C.2.23 Section 5.9 ID selectors
          + C.2.24 Section 5.10 Pseudo-elements and pseudo-classes
          + C.2.25 Section 5.11.2 The link pseudo-classes: :link and
            :visited
          + C.2.26 Section 5.11.4 The language pseudo-class: :lang
          + C.2.27 Section 5.12.1 The :first-line pseudo-element
          + C.2.28 Section 5.12.2 The :first-letter pseudo-element
          + C.2.29 Section 6.1 Specified, computed, and actual values
          + C.2.30 Section 6.4.1 Cascading order
          + C.2.31 Section 6.4.3 Calculating a selector's specificity
          + C.2.32 Section 6.4.4 Precedence of non-CSS presentational
            hints
          + C.2.33 Section 7.3 Recognized Media Types
          + C.2.34 Section 7.3.1 Media Groups
          + C.2.35 Section 8.3 Margin properties
          + C.2.36 Section 8.3.1 Collapsing margins
          + C.2.37 Section 8.4 Padding properties
          + C.2.38 Section 8.5.2 Border color
          + C.2.39 Section 8.5.3 Border style
          + C.2.40 Section 8.6 The box model for inline elements in
            bidirectional context
          + C.2.41 Section 9.1.2 Containing blocks
          + C.2.42 Section 9.2.1.1 Anonymous block boxes
          + C.2.43 Section 9.2.2.1 Anonymous inline boxes
          + C.2.44 Section 9.2.3 Run-in boxes
          + C.2.45 Section 9.2.4 The 'display' property
          + C.2.46 Section 9.3.1 Choosing a positioning scheme
          + C.2.47 Section 9.3.2 Box offsets
          + C.2.48 Section 9.4.1 Block formatting contexts
          + C.2.49 Section 9.4.2 Inline formatting context
          + C.2.50 Section 9.4.3 Relative positioning
          + C.2.51 Section 9.5 Floats
          + C.2.52 Section 9.5.1 Positioning the float
          + C.2.53 Section 9.5.2 Controlling flow next to floats
          + C.2.54 Section 9.7 Relationships between 'display',
            'position', and 'float'
          + C.2.55 Section 9.9 Layered presentation
          + C.2.56 Section 9.10 Text direction
          + C.2.57 Chapter 10 Visual formatting model details
          + C.2.58 Section 10.1 Definition of "containing block"
          + C.2.59 Section 10.2 Content width
          + C.2.60 Section 10.3 Calculating widths and margins
          + C.2.61 Section 10.3.2 Inline, replaced elements
          + C.2.62 Section 10.3.3 Block-level, non-replaced elements in
            normal flow
          + C.2.63 Section 10.3.4 Block-level, replaced elements in normal
            flow
          + C.2.64 Section 10.3.5 Floating, non-replaced elements
          + C.2.65 Section 10.3.6 Floating, replaced elements
          + C.2.66 Section 10.3.7 Absolutely positioned, non-replaced
            elements
          + C.2.67 Section 10.3.8 Absolutely positioned, replaced elements
          + C.2.68 Section 10.4 Minimum and maximum widths
          + C.2.69 Section 10.5 Content height
          + C.2.70 Section 10.6 Calculating heights and margins
          + C.2.71 Section 10.6.1 Inline, non-replaced elements
          + C.2.72 Section 10.6.2 Inline replaced elements, block-level
            replaced elements in normal flow, 'inline-block' replaced
            elements in normal flow and floating replaced elements
          + C.2.73 Section 10.6.3 Block-level non-replaced elements in
            normal flow when 'overflow' computes to 'visible'
          + C.2.74 Section 10.6.4 Absolutely positioned, non-replaced
            elements
          + C.2.75 Section 10.6.5 Absolutely positioned, replaced elements
          + C.2.76 Section 10.7 Minimum and maximum heights
          + C.2.77 Section 10.8 Line height calculations
          + C.2.78 Section 10.8.1 Leading and half-leading
          + C.2.79 Section 11.1 Overflow and clipping
          + C.2.80 Section 11.1.1 Overflow
          + C.2.81 Section 11.1.2 Clipping: the 'clip' property
          + C.2.82 Section 11.2 Visibility
          + C.2.83 Chapter 12 Generated content, automatic numbering, and
            lists
          + C.2.84 Section 12.1 The :before and :after pseudo-elements
          + C.2.85 Section 12.2 The 'content' property
          + C.2.86 Section 12.3.2 Inserting quotes with the 'content'
            property
          + C.2.87 Section 12.4 Automatic counters and numbering
          + C.2.88 Section 12.4.1 Nested counters and scope
          + C.2.89 Section 12.5 Lists
          + C.2.90 Section 12.5.1 Lists
          + C.2.91 Chapter 13 Paged media
          + C.2.92 Section 13.2.2 Page selectors
          + C.2.93 Section 13.3.1 Page break properties
          + C.2.94 Section 13.3.3 Allowed page breaks
          + C.2.95 Section 14.2.1 Background properties
          + C.2.96 Section 14.3 Gamma correction
          + C.2.97 Chapter 15 Fonts
          + C.2.98 Section 15.2 Font matching algorithm
          + C.2.99 Section 15.2.2 Font family
          + C.2.100 Section 15.5 Small-caps
          + C.2.101 Section 15.6 Font boldness
          + C.2.102 Section 15.7 Font size
          + C.2.103 Chapter 16 Text
          + C.2.104 Section 16.2 Alignment
          + C.2.105 Section 16.3.1 Underlining, over lining, striking, and
            blinking
          + C.2.106 Section 16.4 Letter and word spacing
          + C.2.107 Section 16.5 Capitalization
          + C.2.108 Section 16.6 White space
          + C.2.109 Chapter 17 Tables
          + C.2.110 Section 17.2 The CSS table model
          + C.2.111 Section 17.2.1 Anonymous table objects
          + C.2.112 Section 17.4 Tables in the visual formatting model
          + C.2.113 Section 17.4.1 Caption position and alignment
          + C.2.114 Section 17.5 Visual layout of table contents
          + C.2.115 Section 17.5.1 Table layers and transparency
          + C.2.116 Section 17.5.2.1 Fixed table layout
          + C.2.117 Section 17.5.2.2 Automatic table layout
          + C.2.118 Section 17.5.3 Table height algorithms
          + C.2.119 Section 17.5.4 Horizontal alignment in a column
          + C.2.120 Section 17.6 Borders
          + C.2.121 Section 17.6.1 The separated borders model
          + C.2.122 Section 17.6.1.1 Borders and Backgrounds around empty
            cells
          + C.2.123 Section 17.6.2 The collapsing border model
          + C.2.124 Section 17.6.2.1 Border conflict resolution
          + C.2.125 Section 18.1 Cursors: the 'cursor' property
          + C.2.126 Section 18.4 Dynamic outlines
          + C.2.127 Chapter 12 Generated content, automatic numbering, and
            lists
          + C.2.128 Appendix A. Aural style sheets
          + C.2.129 Appendix A Section 5 Pause properties
          + C.2.130 Appendix A Section 6 Cue properties
          + C.2.131 Appendix A Section 7 Mixing properties
          + C.2.132 Appendix B Bibliography
          + C.2.133 Other
     * C.3 Errors
          + C.3.1 Shorthand properties
          + C.3.2 Applies to
          + C.3.3 Section 4.1.1 (and G2)
          + C.3.4 Section 4.1.3 Characters and case
          + C.3.5 Section 4.3 (Double sign problem)
          + C.3.6 Section 4.3.2 Lengths
          + C.3.7 Section 4.3.3 Percentages
          + C.3.8 Section 4.3.4 URLs and URIs
          + C.3.9 Section 4.3.5 Counters
          + C.3.10 Section 4.3.6 Colors
          + C.3.11 Section 4.3.7 Strings
          + C.3.12 Section 5.10 Pseudo-elements and pseudo-classes
          + C.3.13 Section 6.4 The cascade
          + C.3.14 Section 8.1 Box Dimensions
          + C.3.15 Section 8.2 Example of margins, padding, and borders
          + C.3.16 Section 8.5.4 Border shorthand properties
          + C.3.17 Section 9.2.1 Block-level elements and block boxes
          + C.3.18 Section 9.3.1 Choosing a positioning scheme
          + C.3.19 Section 9.3.2 Box offsets
          + C.3.20 Section 9.4.1 Block formatting contexts
          + C.3.21 Section 9.4.2 Inline formatting context
          + C.3.22 Section 9.4.3 Relative positioning
          + C.3.23 Section 9.5 Floats
          + C.3.24 Section 9.5.1 Positioning the float
          + C.3.25 Section 9.5.2 Controlling flow next to floats
          + C.3.26 Section 9.6 Absolute positioning
          + C.3.27 Section 9.7 Relationships between 'display',
            'position', and 'float'
          + C.3.28 Section 9.10 Text direction
          + C.3.29 Section 10.1 Definition of "containing block"
          + C.3.30 Section 10.3.3 Block-level, non-replaced elements in
            normal flow
          + C.3.31 Section 10.4 Minimum and maximum widths
          + C.3.32 Section 10.6.3 Block-level non-replaced elements in
            normal flow when 'overflow' computes to 'visible'
          + C.3.33 Section 10.7 Minimum and maximum heights
          + C.3.34 Section 11.1.1 Overflow
          + C.3.35 Section 11.1.2 Clipping: the 'clip' property
          + C.3.36 Section 11.2 Visibility
          + C.3.37 Section 12.4.2 Counter styles
          + C.3.38 Section 12.6.2 Lists
          + C.3.39 Section 14.2 The background
          + C.3.40 Section 14.2.1 Background properties
          + C.3.41 Section 15.2 Font matching algorithm
          + C.3.42 Section 15.7 Font size
          + C.3.43 Section 16.1 Indentation
          + C.3.44 Section 16.2 Alignment
          + C.3.45 Section 17.2 The CSS table model
          + C.3.46 Section 17.2.1 Anonymous table objects
          + C.3.47 Section 17.4 Tables in the visual formatting model
          + C.3.48 Section 17.5 Visual layout of table contents
          + C.3.49 Section 17.5.1 Table layers and transparency
          + C.3.50 Section 17.6.1 The separated borders model
          + C.3.51 Section 18.2 System Colors
          + C.3.52 Section E.2 Painting order
     * C.4 Clarifications
          + C.4.1 Section 2.1 A brief CSS 2.1 tutorial for HTML
          + C.4.2 Section 2.2 A brief CSS 2.1 tutorial for XML
          + C.4.3 Section 2.3 The CSS 2.1 processing model
          + C.4.4 Section 3.1 Definitions
          + C.4.5 Section 4.1 Syntax
          + C.4.6 Section 4.1.1 Tokenization
          + C.4.7 Section 4.1.3 Characters and case
          + C.4.8 Section 4.1.7 Rule sets, declaration blocks, and
            selectors
          + C.4.9 Section 4.2 Rules for handling parsing errors
          + C.4.10 Section 4.3.1 Integers and real numbers
          + C.4.11 Section 4.3.2 Lengths
          + C.4.12 Section 4.3.4 URLs and URIs
          + C.4.13 Section 5.1 Pattern matching
          + C.4.14 Section 5.7 Adjacent sibling selectors
          + C.4.15 Section 5.8.1 Matching attributes and attribute values
          + C.4.16 Section 5.8.2 Default attribute values in DTDs
          + C.4.17 Section 5.9 ID selectors
          + C.4.18 Section 5.11.3 The dynamic pseudo-classes: :hover,
            :active, and :focus
          + C.4.19 Section 5.11.4 The language pseudo-class: :lang
          + C.4.20 Section 5.12.2 The :first-letter pseudo-element
          + C.4.21 Section 6.2 Inheritance
          + C.4.22 Section 6.2.1 The 'inherit' value
          + C.4.23 Section 6.3 The @import rule
          + C.4.24 Section 6.4 The Cascade
          + C.4.25 Section 6.4.1 Cascading order
          + C.4.26 Section 6.4.3 Calculating a selector's specificity
          + C.4.27 Section 7.2.1 The @media rule
          + C.4.28 Section 7.3 Recognized media types
          + C.4.29 Section 7.3.1 Media groups
          + C.4.30 Section 8.1 Box dimensions
          + C.4.31 Section 8.3 Margin properties
          + C.4.32 Section 8.3.1 Collapsing margins
          + C.4.33 Section 8.5.3 Border style
          + C.4.34 Section 9.1.1 The viewport
          + C.4.35 Section 9.2.4 The 'display' property
          + C.4.36 Section 9.3.1 Choosing a positioning scheme
          + C.4.37 Section 9.3.2 Box offsets
          + C.4.38 Section 9.4.2 Inline formatting context
          + C.4.39 Section 9.4.3 Relative positioning
          + C.4.40 Section 9.5 Floats
          + C.4.41 Section 9.5.1 Positioning the float
          + C.4.42 Section 9.5.2 Controlling flow next to floats
          + C.4.43 Section 9.8 Comparison of normal flow, floats, and
            absolute positioning
          + C.4.44 Section 10.1 Definition of "containing block"
          + C.4.45 Section 10.2 Content width
          + C.4.46 Section 10.3.3 Block-level, non-replaced elements in
            normal flow
          + C.4.47 Section 10.3.8 Absolutely positioning, replaced
            elements
          + C.4.48 Section 10.4 Minimum and maximum widths
          + C.4.49 Section 10.6 Calculating heights and margins
          + C.4.50 Section 10.7 Minimum and maximum heights
          + C.4.51 Section 10.8 Line height calculations
          + C.4.52 Section 10.8.1 Leading and half-leading
          + C.4.53 Section 11.1 Overflow and clipping
          + C.4.54 Section 11.1.1 Overflow
          + C.4.55 Section 11.1.2 Clipping
          + C.4.56 Section 11.2 Visibility
          + C.4.57 Section 12.1 The :before and :after pseudo-elements
          + C.4.58 Section 12.2 The 'content' property
          + C.4.59 Section 12.3.2 Inserting quotes with the 'content'
            property
          + C.4.60 Section 12.4 Automatic counters and numbering
          + C.4.61 Section 12.4.3 Counters in elements with 'display:
            none'
          + C.4.62 Section 14.2 The background
          + C.4.63 Section 15.1 Fonts Introduction
          + C.4.64 Section 15.2 Font matching algorithm
          + C.4.65 Section 15.2.2 Font family
          + C.4.66 Section 15.3.1 Generic font families
          + C.4.67 Section 15.4 Font styling
          + C.4.68 Section 15.5 Small-caps
          + C.4.69 Section 15.6 Font boldness
          + C.4.70 Section 15.7 Font size
          + C.4.71 Section 16.1 Indentation
          + C.4.72 Section 16.2 Alignment
          + C.4.73 Section 16.3.1 Underlining, over lining, striking, and
            blinking
          + C.4.74 Section 16.5 Capitalization
          + C.4.75 Section 16.6 White space
          + C.4.76 Section 17.1 Introduction to tables
          + C.4.77 Section 17.2 The CSS table model
          + C.4.78 Section 17.2.1 Anonymous table objects
          + C.4.79 Section 17.4 Tables in the visual formatting model
          + C.4.80 Section 17.5 Visual layout of table contents
          + C.4.81 Section 17.5.1 Table layers and transparency
          + C.4.82 Section 17.5.2 Table width algorithms
          + C.4.83 Section 17.5.2.1 Fixed table layout
          + C.4.84 Section 17.5.2.2 Automatic table layout
          + C.4.85 Section 17.5.4 Horizontal alignment in a column
          + C.4.86 Section 17.5.5 Dynamic row and column effects
          + C.4.87 Section 17.6.1 The separated borders model
          + C.4.88 Section 17.6.2 The collapsing borders model
          + C.4.89 Section 18.2 System Colors
          + C.4.90 Section 18.4 Dynamic outlines
          + C.4.91 Section 18.4.1 Outlines and the focus
          + C.4.92 Appendix D Default style sheet for HTML 4
     * C.5 Errata since the Candidate Recommendation of July 2007
          + C.5.1 Section 1.4.2.1 Value
          + C.5.2 Section 2.3 The CSS 2.1 processing model
          + C.5.3 Section 3.1 Definitions
          + C.5.4 Section 4.1.1 Tokenization
          + C.5.5 Section 4.1.2.2 Informative Historical Notes
          + C.5.6 Section 4.1.3 Characters and case
          + C.5.7 Section 4.1.3 Characters and case
          + C.5.8 Section 4.1.3 Characters and case
          + C.5.9 Section 4.1.3 Characters and case
          + C.5.10 Section 4.1.5 At-rules
          + C.5.11 Section 4.1.7 Rule sets, declaration blocks, and
            selectors
          + C.5.12 Section 4.2 Rules for handling parsing errors
          + C.5.13 Section 4.2 Rules for handling parsing errors
          + C.5.14 Section 4.3.2 Lengths
          + C.5.15 Section 4.3.5 Counters
          + C.5.16 Section 5.8.1 Matching attributes and attribute values
          + C.5.17 Section 5.8.2 Default attribute values in DTDs
          + C.5.18 Section 5.11.4 The language pseudo-class: :lang
          + C.5.19 Section 5.12.3 The :before and :after pseudo-elements
          + C.5.20 Section 6.3 The @import rule
          + C.5.21 Section 6.3 The @import rule
          + C.5.22 Section 6.4.1 Cascading order
          + C.5.23 Section 6.4.1 Cascading order
          + C.5.24 Section 7.2.1 The @media rule
          + C.5.25 Section 8.3.1 Collapsing margins
          + C.5.26 Section 8.3.1 Collapsing margins
          + C.5.27 Section 8.3.1 Collapsing margins
          + C.5.28 Section 9.2.2 Inline-level elements and inline boxes
          + C.5.29 Section 9.2.4 The 'display' property
          + C.5.30 Section 9.3.2 Box offsets: 'top', 'right', 'bottom',
            'left'
          + C.5.31 Section 9.5 Floats
          + C.5.32 Section 9.5 Floats
          + C.5.33 Section 9.5.2 Controlling flow next to floats: the
            'clear' property
          + C.5.34 Section 9.6.1 Fixed positioning
          + C.5.35 Section 9.9.1 Specifying the stack level: the 'z-index'
            property
          + C.5.36 Section 10.1 Definition of "containing block"
          + C.5.37 Section 10.3 Calculating widths and margins
          + C.5.38 Section 10.3.1 Inline, non-replaced elements
          + C.5.39 Section 10.3.2 Inline, replaced elements
          + C.5.40 Section 10.3.2 Inline, replaced elements
          + C.5.41 Section 10.3.3 Block-level, non-replaced elements in
            normal flow
          + C.5.42 Section 10.3.7 Absolutely positioned, non-replaced
            elements
          + C.5.43 Section 10.3.7 Absolutely positioned, non-replaced
            elements
          + C.5.44 Section 10.3.8 Absolutely positioned, replaced elements
          + C.5.45 Section 10.3.8 Absolutely positioned, replaced elements
          + C.5.46 Section 10.3.8 Absolutely positioned, replaced elements
          + C.5.47 Section 10.5 Content height: the 'height' property
          + C.5.48 Section 10.6.2 Inline replaced elements […]
          + C.5.49 Section 10.6.4 Absolutely positioned, non-replaced
            elements
          + C.5.50 Section 10.6.5 Absolutely positioned, replaced elements
          + C.5.51 Section 10.8.1 Leading and half-leading
          + C.5.52 Section 11.1.1 Overflow: the 'overflow' property
          + C.5.53 Section 11.1.2 Clipping: the 'clip' property
          + C.5.54 Section 12.2 The 'content' property
          + C.5.55 Section 12.4.2 Counter styles
          + C.5.56 Section 12.5 Lists
          + C.5.57 Section 12.5.1 Lists: the 'list-style-type',
            'list-style-image', 'list-style-position', and 'list-style'
            properties
          + C.5.58 Section 12.5.1 Lists: the 'list-style-type',
            'list-style-image', 'list-style-position', and 'list-style'
            properties
          + C.5.59 Section 12.5.1 Lists: the 'list-style-type',
            'list-style-image', 'list-style-position', and 'list-style'
            properties
          + C.5.60 Section 13.2 Page boxes: the @page rule
          + C.5.61 Section 13.2.1.1 Rendering page boxes that do not fit a
            target sheet
          + C.5.62 Section 13.2.3 Content outside the page box
          + C.5.63 Section 13.3.1 Page break properties:
            'page-break-before', 'page-break-after', 'page-break-inside'
          + C.5.64 Section 13.3.1 Page break properties:
            'page-break-before', 'page-break-after', 'page-break-inside'
          + C.5.65 Section 13.3.2 Breaks inside elements: 'orphans',
            'widows'
          + C.5.66 Section 13.3.2 Breaks inside elements: 'orphans',
            'widows'
          + C.5.67 Section 13.3.3 Allowed page breaks
          + C.5.68 Section 13.3.3 Allowed page breaks
          + C.5.69 Section 13.3.3 Allowed page breaks
          + C.5.70 Section 13.3.5 "Best" page breaks
          + C.5.71 Section 14.2 The background
          + C.5.72 Section 14.2 The background
          + C.5.73 Section 14.2.1 Background properties:
            'background-color', 'background-image', 'background-repeat',
            'background-attachment', 'background-position', and
            'background'
          + C.5.74 Section 15.6 Font boldness: the 'font-weight' property
          + C.5.75 Section 16.6 Whitespace: the 'white-space' property
          + C.5.76 Section 16.6.1 The 'white-space' processing model
          + C.5.77 Section 17.2.1 Anonymous table objects
          + C.5.78 Section 17.2.1 Anonymous table objects
          + C.5.79 Section 17.4 Tables in the visual formatting model
          + C.5.80 Section 17.5.4 Horizontal alignment in a column
          + C.5.81 Section 18.1 Cursors: the 'cursor' property
          + C.5.82 Section B.2 Informative references
          + C.5.83 Appendix D. Default style sheet for HTML 4
          + C.5.84 Appendix D. Default style sheet for HTML 4
          + C.5.85 Section E.2 Painting order
          + C.5.86 Appendix G. Grammar of CSS 2.1
          + C.5.87 Section G.1 Grammar
          + C.5.88 Section G.2 Lexical scanner
          + C.5.89 Section G.2 Lexical scanner
          + C.5.90 Section G.2 Lexical scanner
          + C.5.91 Section G.2 Lexical scanner
          + C.5.92 Appendix I. Index
     * C.6 Errata since the Candidate Recommendation of April 2009
          + C.6.1 Section 4.2 Rules for handling parsing errors
          + C.6.2 Section 13.3.3 Allowed page breaks
          + C.6.3 Section 15.3 Font family: the 'font-family' property
          + C.6.4 Section 15.3.1.1 serif
          + C.6.5 Section 15.7 Font size: the 'font-size' property
          + C.6.6 Section 17.5.2.1 Fixed table layout
          + C.6.7 Section 17.5.3 Table height layout
          + C.6.8 Appendix G. Grammar of CSS 2.1
     * C.7 Errata since the Candidate Recommendation of September 2009
          + C.7.1 Section 1.4.2.1 Value
          + C.7.2 Section 3.1 Definitions
          + C.7.3 Section 4.1.1 Tokenization
          + C.7.4 Section 4.1.1 Tokenization
          + C.7.5 Section 4.1.1 Tokenization
          + C.7.6 Section 4.1.1 Tokenization
          + C.7.7 Section 4.1.2.2 Informative Historical Notes
          + C.7.8 Section 4.1.3 Characters and case
          + C.7.9 Section 4.1.3 Characters and case
          + C.7.10 Section 4.1.8 Declarations and properties
          + C.7.11 Section 4.2 Rules for handling parsing errors
          + C.7.12 Section 4.3.2 Lengths
          + C.7.13 Section 4.3.2 Lengths
          + C.7.14 Section 4.3.4 URLs and URIs
          + C.7.15 Section 4.3.4 URLs and URIs
          + C.7.16 Section 5.8.2 Default attribute values in DTDs
          + C.7.17 Section 5.11.4 The language pseudo-class: :lang
          + C.7.18 Section 5.12 Pseudo-elements
          + C.7.19 Section 5.12.1 The :first-line pseudo-element
          + C.7.20 Section 5.12.2 The :first-letter pseudo-element
          + C.7.21 Section 6.2 Inheritance
          + C.7.22 Section 6.4.4 Precedence of non-CSS presentational
            hints
          + C.7.23 Section 7.3 Recognized media types
          + C.7.24 Section 8.3.1 Collapsing margins
          + C.7.25 Section 8.3.1 Collapsing margins
          + C.7.26 Section 9.2.1 Block-level elements and block boxes
          + C.7.27 Section 9.2.1.1 Anonymous block boxes
          + C.7.28 Section 9.2.1.1 Anonymous block boxes
          + C.7.29 Section 9.2.1.1 Anonymous block boxes
          + C.7.30 Section 9.2.1.1 Anonymous block boxes
          + C.7.31 Section 9.2.2 Inline-level elements and inline boxes
          + C.7.32 Section 9.2.3 Run-in boxes
          + C.7.33 Section 9.2.4 The 'display' property
          + C.7.34 Section 9.2.4 The 'display' property
          + C.7.35 Section 9.3 Positioning schemes
          + C.7.36 Section 9.4 Normal flow
          + C.7.37 Section 9.3.2 Box offsets: 'top', 'right', 'bottom',
            'left'
          + C.7.38 Section 9.5 Floats
          + C.7.39 Section 9.5 Floats
          + C.7.40 Section 9.5.2 Controlling flow next to floats: the
            'clear' property
          + C.7.41 Section 9.5.2 Controlling flow next to floats: the
            'clear' property
          + C.7.42 Section 9.5.2 Controlling flow next to floats: the
            'clear' property
          + C.7.43 Section 9.5.2 Controlling flow next to floats: the
            'clear' property
          + C.7.44 Section 14.2.1 Background properties
          + C.7.45 Section 9.9.1 Specifying the stack level: the 'z-index'
            property
          + C.7.46 Section 9.10 Text direction: the 'direction' and
            'unicode-bidi' properties
          + C.7.47 Section 9.10 Text direction: the 'direction' and
            'unicode-bidi' properties
          + C.7.48 Section 9.10 Text direction: the 'direction' and
            'unicode-bidi' properties
          + C.7.49 Section 10.1 Definition of "containing block"
          + C.7.50 Section 10.2 Content width: the 'width' property
          + C.7.51 Section 10.2 Content width: the 'width' property
          + C.7.52 Section 10.2 Content width: the 'width' property
          + C.7.53 Section 10.5 Content height: the 'height' property
          + C.7.54 Section 10.5 Content height: the 'height' property
          + C.7.55 Section 10.6.7 'Auto' heights for block formatting
            context roots
          + C.7.56 Section 10.7 Minimum and maximum heights: 'min-height'
            and 'max-height'
          + C.7.57 Section 10.8 Line height calculations: the
            'line-height' and 'vertical-align' properties
          + C.7.58 Section 10.8 Line height calculations: the
            'line-height' and 'vertical-align' properties
          + C.7.59 Section 10.8.1 Leading and half-leading
          + C.7.60 Section 10.8.1 Leading and half-leading
          + C.7.61 Section 10.8.1 Leading and half-leading
          + C.7.62 Section 11.1 Overflow and clipping
          + C.7.63 Section 11.1.1 Overflow: the 'overflow' property
          + C.7.64 Section 11.1.1 Overflow: the 'overflow' property
          + C.7.65 Section 11.1.1 Overflow: the 'overflow' property
          + C.7.66 Section 11.1.2 Clipping: the 'clip' property
          + C.7.67 Section 12.5 Lists
          + C.7.68 Section 12.5.1 Lists: the 'list-style-type',
            'list-style-image', 'list-style-position', and 'list-style'
            properties
          + C.7.69 Section 12.5.1 Lists: the 'list-style-type',
            'list-style-image', 'list-style-position', and 'list-style'
            properties
          + C.7.70 Section 12.5.1 Lists: the 'list-style-type',
            'list-style-image', 'list-style-position', and 'list-style'
            properties
          + C.7.71 Section 12.5.1 Lists: the 'list-style-type',
            'list-style-image', 'list-style-position', and 'list-style'
            properties
          + C.7.72 Section 12.5.1 Lists: the 'list-style-type',
            'list-style-image', 'list-style-position', and 'list-style'
            properties
          + C.7.73 Section 13.2 Page boxes: the @page rule
          + C.7.74 Section 13.2.2 Page selectors: selecting left, right,
            and first pages
          + C.7.75 Section 13.3.2 Breaks inside elements: 'orphans',
            'widows'
          + C.7.76 Section 13.3.3 Allowed page breaks
          + C.7.77 Section 15.3 Font family: the 'font-family' property
          + C.7.78 Section 15.3.1 Generic font families
          + C.7.79 Section 15.6 Font boldness: the 'font-weight' property
          + C.7.80 Section 15.6 Font boldness: the 'font-weight' property
          + C.7.81 Section 15.7 Font size: the 'font-size' property
          + C.7.82 Section 16.1 Indentation: the 'text-indent' property
          + C.7.83 Section 16.1 Indentation: the 'text-indent' property
          + C.7.84 Section 16.2 Alignment: the 'text-align' property
          + C.7.85 Section 16.2 Alignment: the 'text-align' property
          + C.7.86 Section 16.3.1 Underlining, overlining, striking, and
            blinking: the 'text-decoration' property
          + C.7.87 Section 16.3.1 Underlining, overlining, striking, and
            blinking: the 'text-decoration' property
          + C.7.88 Section 16.4 Letter and word spacing: the
            'letter-spacing' and 'word-spacing' properties
          + C.7.89 Section 16.6 White space: the 'white-space' property
          + C.7.90 Section 16.6.1 The 'white-space' processing model
          + C.7.91 Section 16.6.1 The 'white-space' processing model
          + C.7.92 Section 16.6.1 The 'white-space' processing model
          + C.7.93 Section 17.2 The CSS table model
          + C.7.94 Section 17.2.1 Anonymous table objects
          + C.7.95 Section 17.2.1 Anonymous table objects
          + C.7.96 Section 17.4 Tables in the visual formatting model
          + C.7.97 Section 17.4 Tables in the visual formatting model
          + C.7.98 Section 17.5.2.2 Automatic table layout
          + C.7.99 Section 17.5.3 Table height algorithms
          + C.7.100 Section 17.5.4 Horizontal alignment in a column
          + C.7.101 Section B.2 Informative references
          + C.7.102 Section D. Default style sheet for HTML 4
          + C.7.103 Section E.2 Painting order
          + C.7.104 Appendix G Grammar of CSS 2.1
     * C.8 Changes since the working draft of 7 December 2010
          + C.8.1 8.3.1 Collapsing margins
          + C.8.2 10.8.1 Leading and half-leading
          + C.8.3 10.3 Calculating widths and margins
          + C.8.4 14.3 Gamma correction
          + C.8.5 11.1.2 Clipping: the 'clip' property
          + C.8.6 9.4.2 Inline formatting contexts
          + C.8.7 10.3.2 Inline, replaced elements
          + C.8.8 10.1 Definition of "containing block"
          + C.8.9 13.2.2 Page selectors: selecting left, right, and first
            pages
          + C.8.10 8.3.1 Collapsing margins
          + C.8.11 10.8 Line height calculations: the 'line-height' and
            'vertical-align' properties
          + C.8.12 10.8.1 Leading and half-leading
          + C.8.13 10.6.1 Inline, non-replaced elements
          + C.8.14 9.5.1 Positioning the float: the 'float' property
          + C.8.15 9.2.1.1 Anonymous block boxes
          + C.8.16 5.12.1 The :first-line pseudo-element
          + C.8.17 16.6 White space: the 'white-space' property
          + C.8.18 12.5.1 Lists: the 'list-style-type',
            'list-style-image', 'list-style-position', and 'list-style'
            properties
          + C.8.19 9.7 Relationships between 'display', 'position', and
            'float'
          + C.8.20 9.4.2 Inline formatting contexts
          + C.8.21 4.1.9 Comments
          + C.8.22 12.5.1 Lists: the 'list-style-type',
            'list-style-image', 'list-style-position', and 'list-style'
            properties
          + C.8.23 9.5.1 Positioning the float: the 'float' property
          + C.8.24 9.3 Positioning schemes
          + C.8.25 9.10 Text direction: the 'direction' and 'unicode-bidi'
            properties
          + C.8.26 16.3.1 Underlining, overlining, striking, and blinking:
            the 'text-decoration' property
          + C.8.27 16.3.1 Underlining, overlining, striking, and blinking:
            the 'text-decoration' property
          + C.8.28 10.4 Minimum and maximum widths: 'min-width' and
            'max-width'
          + C.8.29 9.3.2 Box offsets: 'top', 'right', 'bottom', 'left'
          + C.8.30 9.2.1.1 Anonymous block boxes
          + C.8.31 17.4 Tables in the visual formatting model
          + C.8.32 11.1.2 Clipping: the 'clip' property
          + C.8.33 13.2 Page boxes: the @page rule
          + C.8.34 4.1.1 Tokenization
          + C.8.35 4.2 Rules for handling parsing errors
          + C.8.36 3.1 Definitions
          + C.8.37 4.3.4 URLs and URIs
          + C.8.38 9.5 Floats
          + C.8.39 11.1.1 Overflow: the 'overflow' property
          + C.8.40 9.2.1.1 Anonymous block boxes
          + C.8.41 16.2 Alignment: the 'text-align' property
          + C.8.42 9.5 Floats
          + C.8.43 9.4.2 Inline formatting contexts
          + C.8.44 5.12 Pseudo-elements
          + C.8.45 9.5 Floats
          + C.8.46 9.5 Floats
          + C.8.47 14.2.1 Background properties: 'background-color',
            'background-image', 'background-repeat',
            'background-attachment', 'background-position', and
            'background'
          + C.8.48 9.2.4 The 'display' property
          + C.8.49 6.1.2 Computed values
          + C.8.50 10.3.2 Inline, replaced elements
          + C.8.51 Section 9.5.2 Controlling flow next to floats: the
            'clear' property
          + C.8.52 G.2 Lexical scanner
          + C.8.53 Section 9.5.2 Controlling flow next to floats: the
            'clear' property
          + C.8.54 9.5 Floats
          + C.8.55 10.6.3 Block-level non-replaced elements in normal flow
            when 'overflow' computes to 'visible'

   This appendix is informative, not normative.

   CSS 2.1 is an updated revision of CSS2. The changes between the CSS2
   specification (see [CSS2]) and this specification fall into five
   groups: known errors, typographical errors, clarifications, changes and
   additions. Typographical errors are not listed here.

   In addition, this chapter lists the errata (part 1 and part 2) that
   were subsequently applied to CSS 2.1 since it became a Candidate
   Recommendation in July 2007.

   This chapter is not a complete list of changes. Minor editorial changes
   and most changes to examples are also not listed here.

C.1 Additional property values

  C.1.1 Section 4.3.6 Colors

   New color value: 'orange'

  C.1.2 Section 9.2.4 The 'display' property

   New 'display' value: 'inline-block'

  C.1.3 Section 12.2 The 'content' property

   New 'content' values 'none' and 'normal'. (The values 'none' and
   'normal' are equivalent in CSS 2.1, but may have different functions in
   CSS3.)

  C.1.4 Section 16.6 White space: the 'white-space' property

   New 'white-space' values: 'pre-wrap' and 'pre-line'

  C.1.5 Section 18.1 Cursors: the 'cursor' property

   New 'cursor' value: 'progress'

C.2 Changes

  C.2.1 Section 1.1 CSS 2.1 vs CSS 2

   This new section is added to explain the motivation for CSS2.1 and its
   relation to CSS2.

  C.2.2 Section 1.2 Reading the specification

   This section (formerly Section 1.1) has been marked non-normative.

  C.2.3 Section 1.3 How the specification is organized

   This section (formerly Section 1.2) has been marked non-normative.

  C.2.4 Section 1.4.2.1 Value

   This section (formerly unnumbered under 1.3.2) notes that value types
   are specified in terms of tokens and that spaces may appear between
   tokens in values. A note explains that spaces are required between some
   tokens.

  C.2.5 Section 1.4.2.6 Media groups

   This section (formerly unnumbered under 1.3.2) now declares the Media
   line in property definitions to be non-normative.

  C.2.6 Section 1.4.2.7 Computed value

   A new line is added to each property definition specifying what the
   computed values are for the property. (This defines what level of
   computation is done to a property value before inheritance and before
   certain other calculations.)

  C.2.7 Section 1.4.4 Notes and examples

   This section (formerly 1.3.4) now specifies that HTML examples lacking
   DOCTYPE declarations are SGML Text Entities conforming to the HTML 4.01
   Strict DTD [HTML4]. The markup for many examples has been reformulated
   to either include a DOCTYPE or conform to this definition.

  C.2.8 Section 1.5 Acknowledgments

   This section (formerly 1.4) has been updated to reflect contributions
   to CSS2.1 and has been marked non-normative.

  C.2.9 Section 3.2 Conformance

   Support for user style sheets is now required (in most cases), rather
   than just recommended.

   Support for turning of author style sheets is now required.

   Application of CSS properties to form controls is explicitly undefined.
   Authors are recommended to treat form control styling capabilities in
   UAs as experimental.

  C.2.10 Section 3.3 Error Conditions

   This section changed to say that error handling is specified in most
   cases.

  C.2.11 Section 4.1.1 Tokenization

   Added INVALID token and rules for its definition.

   An optional hyphen, "-", is now allowed at the beginning of an "ident"
   for vendor extensions. (See section 4.1.2.1)

   The underscore character ("_") is allowed in identifiers. The
   definitions of the lexical macros "nmstart" and "nmchar" now include
   it. See also section 4.1.2.1 (Vendor extensions).

   The "escape" macro has been modified to allow the escaping of any
   character except newlines, form feeds, and hex digits (to avoid
   conflict with Unicode escapes).

   Modified "string1" and "string2" macros by defining allowed characters
   through excluding disallowed characters. This allows invisible ASCII
   characters to be included in a string.

  C.2.12 Section 4.1.3 Characters and case

   Updated prose about identifiers (second bullet point) to match changes
   in the tokenization (above).

   Excluded null (0x0) character from CSS numerical escapes and indicate
   that it is undefined in CSS2.1 what happens if such a character is
   encountered.

   Allowed the use of U+FFFD as a replacement for characters outside the
   range allowed by Unicode.

   CSS is no longer case-insensitive, but case-sensitive with exceptions.
   Changed "All CSS style sheets are case-insensitive, except for parts
   that are not under the control of CSS" to "All CSS syntax is
   case-insensitive within the ASCII range (i.e., [a-z] and [A-Z] are
   equivalent), except for parts that are not under the control of CSS."
   See also the change to case-sensitivity of counters in 4.3.5.

  C.2.13 Section 4.2 Rules for handling parsing errors

   Defined parsing in the cases of Malformed Declarations, Unexpected End
   of Stylesheet, and Unexpected End of String.

  C.2.14 Section 4.3 Values

   Sections 4.3.7 (Angles), 4.3.8 (Times), and 4.3.9 (Frequencies) have
   been moved to the informative Appendix A.

  C.2.15 Section 4.3.2 Lengths

   Added a paragraph on heuristics for finding the x-height of a font.

  C.2.16 Section 4.3.4 URLs and URIs

   Updated URI references to RFC3986.

  C.2.17 Section 4.3.5 Counters

   Changed "Counters are denoted by identifiers" to "Counters are denoted
   by [INS: case-sensitive :INS] identifiers" (see also the change to
   case-sensitivity in 4.1.3).

  C.2.18 Section 4.3.6 Colors

   Defined the numeric values corresponding to color keywords instead of
   referencing HTML4 for those values.

   UAs are now allowed to intelligently map colors outside the gamut into
   the gamut instead of simply clipping them into the range of the gamut.

  C.2.19 Section 4.3.8 Unsupported Values

   Added this section to recommend that unsupported properties and values
   be ignored as if they were invalid.

  C.2.20 Section 4.4 CSS style sheet representation

   Changed character encoding detection rule 2 to include a BOM and
   referred to additional rules below.

   Added rule 4 to provide for use of the referring style sheet or
   document's character encoding.

   Added rule 5 to require falling back to UTF-8.

   Removed the restriction on using @charset in embedded style sheets.

   Allowed a BOM to precede the @charset rule.

   Added requirement that @charset rule must be a literal
   '@charset"...";', not a CSS-syntax equivalent.

   Added requirement to support for UTF-8 at minimum.

   Specified that any @charset rule not at the beginning of the style
   sheet must be ignored.

   Removed note on theoretical problem with @charset problem and precisely
   defined rules for character encoding detection based on @charset and/or
   BOM.

   Specified that UAs must ignore style sheets in unknown encodings.

  C.2.21 Section 5.8.1 Matching attributes and attribute values

   BCP 47 replaces RFC 1766.

  C.2.22 Section 5.8.3 Class selectors

   Class selectors are allowed for other formats than HTML.

   Added a note about matching classes in formats with multiple class
   attributes per element. The behavior is non-normative, because, at the
   time of writing, there exist no such formats.

  C.2.23 Section 5.9 ID selectors

   Specified how to match elements with two or more ID attributes.

  C.2.24 Section 5.10 Pseudo-elements and pseudo-classes

   Removed exception for HTML UAs that allowed them (and only them) to
   ignore ':first-letter' and ':first-line'.

  C.2.25 Section 5.11.2 The link pseudo-classes: :link and :visited

   UAs may return a :visited link to :link status at some point. (This was
   previously a note, but is now normative.)

   Added a note about privacy concerns with link pseudo classes and
   allowed UAs to treat :visited as :link.

  C.2.26 Section 5.11.4 The language pseudo-class: :lang

   The identifier C in ':lang(C)' need not be a valid language code, but
   it must not be empty.

  C.2.27 Section 5.12.1 The :first-line pseudo-element

   ':first-line' also applies to inline blocks, table captions and table
   cells. Added a definition of "first formatted line" to make the rules
   about which line is the first line more precise.

   UAs are no longer forbidden from applying more properties than the
   given list.

  C.2.28 Section 5.12.2 The :first-letter pseudo-element

   More precise definition of first letter. Added rules for cases where
   the first letter is in an inline block or table cell. Added rules for
   cases when preceding punctuation is in a different element from the
   first letter itself.

   UAs may apply other properties to first letters than the given list.

   Unicode character classes Pi and Pf added to the definition of
   punctuation.

  C.2.29 Section 6.1 Specified, computed, and actual values

   Redefined "computed value" and created the concept of "used value" so
   that inheritance can be performed without laying out the document. This
   change has the effect of allowing (requiring) percentages to be
   inherited as percentages and affects many other layout calculations
   throughout the spec.

   Since computed value of a property can now also be a percentage. In
   particular, the following properties now inherit the percentage if the
   specified value is a percentage:
     * background-position
     * bottom, left, right, top
     * height, width
     * margin-bottom, margin-left, margin-right, margin-top,
     * min-height, min-width
     * padding-bottom, padding-left, padding-right, padding-top
     * text-indent

   Note that only 'text-indent' inherits by default, the others only
   inherit if the 'inherit' keyword is specified.

  C.2.30 Section 6.4.1 Cascading order

   Changed suggestion that user be able to turn off author styles to a
   requirement.

  C.2.31 Section 6.4.3 Calculating a selector's specificity

   The "style" attribute now has a higher specificity than any style rule.

   Pseudo-elements are now counted with elements in calculating a a
   selector's specificity.

  C.2.32 Section 6.4.4 Precedence of non-CSS presentational hints

   "Non-CSS presentational hints" no longer exist, with the exception of a
   small set of attributes in HTML.

  C.2.33 Section 7.3 Recognized Media Types

   Added 'speech' media type.

   Marked "Media" field in property descriptions informative.

  C.2.34 Section 7.3.1 Media Groups

   Marked this section informative.

   Added sound to 'handheld' in media type/media group table.

   Changed 'tactile' to be both 'static' and 'interactive'.

  C.2.35 Section 8.3 Margin properties

   If the containing block's width depends on an element with percentage
   margins, then the resulting layout is undefined in CSS 2.1.

  C.2.36 Section 8.3.1 Collapsing margins

   In the definition of "collapsing margins", added "non-empty content"
   and "clearance" to the parenthetical list of things that prevent
   consecutive margins from being adjoining.

   Vertical margins of elements with 'overflow' other than 'visible' no
   longer collapse with their in-flow children.

   Defined how margins collapse through an element with adjoining top and
   bottom margins.

   Added that margins of the root element's box do not collapse.

   More rigorously defined "adjoining" for margin collapsing.

   Sixth bullet, second sub-bullet: to find the position of the top border
   edge, assume the element has a bottom (rather than top) border.

   Margins of relatively positioned elements do sometimes collapse.

  C.2.37 Section 8.4 Padding properties

   If the containing block's width depends on an element with percentage
   padding, then the resulting layout is undefined in CSS 2.1.

  C.2.38 Section 8.5.2 Border color

   'transparent' can now be specified independently for each border side,
   on par with <color>.

  C.2.39 Section 8.5.3 Border style

   3D border styles ('groove', 'ridge', 'inset', 'outset') now depend on
   the corresponding border-color rather than on 'color'.

  C.2.40 Section 8.6 The box model for inline elements in bidirectional context

   Added this new section to specify layout of inline boxes when affected
   by bidi.

  C.2.41 Section 9.1.2 Containing blocks

   Removed paragraphs about the initial containing block, as this is now
   defined differently. (See changes to section 10.1.)

  C.2.42 Section 9.2.1.1 Anonymous block boxes

   Added a paragraph to define formatting when an inline box contains a
   block box.

   Specified what property values are applied to anonymous boxes.

  C.2.43 Section 9.2.2.1 Anonymous inline boxes

   Specified that collapsed white space does not generate anonymous inline
   boxes.

  C.2.44 Section 9.2.3 Run-in boxes

   Changed run-in rules so that a) run-ins that contain blocks become
   blocks b) run-ins can only run into sibling blocks and c) run-ins
   cannot run into other run-ins.

  C.2.45 Section 9.2.4 The 'display' property

   The 'marker' and 'compact' values of the 'display' property are not
   part of CSS 2.1. Text relating to these values has been removed
   throughout the specification.

   Defined the computed value of 'display' as the specified value except
   for positioned and floating elements and for the root element. The
   computed value of 'display' for these elements is defined in section
   9.7 and is slightly different from the definition in CSS2.

   Conforming HTML UAs are no longer allowed to ignore the 'display'
   property.

  C.2.46 Section 9.3.1 Choosing a positioning scheme

   The 'position' property now applies to all elements, including
   generated content.

   The effect of relative positioning on table captions and internal table
   elements is undefined in CSS 2.1.

   For fixed positioning, introduced a conflict between this section and
   section 10.1 rule 3. See howcome [member-only] for rationale.

   Forbid UAs from paginating the content of fixed boxes.

   UAs are allowed to treat all values of 'position' as 'static' on the
   root element.

  C.2.47 Section 9.3.2 Box offsets

   Defined computed values of 'top', 'right', 'bottom', 'left' based on
   the value of 'position'.

   Percentage offsets are no longer undefined for containing blocks
   without an explicit height.

  C.2.48 Section 9.4.1 Block formatting contexts

   Specified that floats, absolutely positioned elements, inline-blocks,
   table-cells, table-captions, and elements with 'overflow' other than
   'visible' establish new block formatting contexts.

   In the paragraph about the position of a box's outer edge with respect
   to its containing block, except boxes that establish a new block
   formatting context, as they may become narrower due to floats.

  C.2.49 Section 9.4.2 Inline formatting context

   Specified that the effect of 'justify' on the content of a line box
   does not affect the contents of inline-table and inline-block boxes.

   Empty line boxes are now required to be treated as zero-height and
   ignored in margin collapsing.

  C.2.50 Section 9.4.3 Relative positioning

   Added several paragraphs and an example to explain exactly what the
   computed values of relatively-positioned offsets are, how they affect
   each other, and what happens when the positioning is overconstrained.
   (These were not previously defined.)

  C.2.51 Section 9.5 Floats

   Floats are no longer required to have an explicit width.

   Floats outside of line boxes no longer align to the bottom of the
   preceding block box; it is implied that they are initially aligned with
   their non-floated position.

   Specified that "If a shortened line box is too small to contain any
   further content, then it is shifted downward until either it fits or
   there are no more floats present."

   Specified that the border box of a table, block-level replaced element,
   or element in the normal flow that establishes a new block formatting
   context must not overlap any floats in the same block formatting
   context.

  C.2.52 Section 9.5.1 Positioning the float

   The 'float' property now also applies to :before/:after and generated
   content.

   UAs are now allowed to treat all values of float as 'none' on the root
   element.

   Added to rule 4 prose to define the position of a float when it occurs
   between two collapsing margins.

  C.2.53 Section 9.5.2 Controlling flow next to floats

   Defined clearance to precisely detail the 'clear' property's effect on
   margin collapsing and the block's cleared position.

   Added note to explain effect of 'clear' on inline elements since CSS1
   (but not CSS2 or CSS 2.1) allows 'clear' on inline elements.

  C.2.54 Section 9.7 Relationships between 'display', 'position', and 'float'

   Changed rules to convert 'display' not always to 'block', but to an
   appropriate block-level display value as given by a mapping table.

   Added rule 4 to convert root element's 'display' value according to the
   mapping.

  C.2.55 Section 9.9 Layered presentation

   Specified that the background and borders of an element that forms a
   stacking context are behind all of its descendants, altered stacking
   context prose to be more precise, and added a normative Appendix E:
   Elaborate description of Stacking Contexts to be even more precise
   about the position of borders, backgrounds, and content on the z-axis.

  C.2.56 Section 9.10 Text direction

   Conforming UAs are now allowed to not support bidirectional text; in
   this case they must ignore the 'direction' and 'unicode-bidi'
   properties. However since applying bidi can have an effect even when a
   document does not contain right-to-left characters, UAs that do support
   bidi are no longer permitted to not apply the algorithm just because
   the document lacks right-to-left characters.

   Added a paragraph to define precisely how the Unicode bidirectional
   algorithm applies to text in the CSS formatting model and how the CSS
   'direction' property on blocks maps into the algorithm.

   Conforming HTML UAs are no longer exempt from supporting 'direction'
   and 'unicode-bidi'.

  C.2.57 Chapter 10 Visual formatting model details

   Updated prose to use the terms "specified", "computed" and "used" as
   appropriate when referencing values. This affects many calculations in
   this section. (See changes to section 6.1.)

  C.2.58 Section 10.1 Definition of "containing block"

   In rule 1, defined the initial containing block as the viewport for
   continuous media and the page area for paged media. (It was previously
   undefined.)

   In rule 2, defined the page area as the containing block for fixed
   positioned elements in paged media.

   In rule 4.1, when the containing block of an absolutely-positioned
   element is formed by an inline-level element, it is now formed by that
   element's padding edges, not its content edges.

   In rule 4, changed the containing block for absolutely positioned
   elements with only statically positioned elements from the root's
   content box to the initial containing block.

   Specified the positioning and breaking behavior of
   absolutely-positioned elements in paged media.

  C.2.59 Section 10.2 Content width

   Declared that if the containing block's width depends on an element's
   percentage width, then the resulting layout is undefined in CSS 2.1.

  C.2.60 Section 10.3 Calculating widths and margins

   The computed values of 'left' and 'right' for are now defined in
   section 9.3.2. The value 'auto' does not always compute to zero.

   Added sections 10.3.9 and 10.3.10 to define calculations for inline
   blocks.

  C.2.61 Section 10.3.2 Inline, replaced elements

   The sizing algorithm for replaced elements now takes into account and
   attempts to preserve the replaced content's intrinsic ratio. Sizing of
   replaced elements with percentage intrinsic sizes and without intrinsic
   sizes is now also defined.

   The effect of percentage intrinsic widths is now undefined for CSS
   level 2, rather than ignored.

  C.2.62 Section 10.3.3 Block-level, non-replaced elements in normal flow

   Specified that a computed total of the width, padding, and borders that
   is greater than the containing block width causes auto margins to be
   treated as zero in the rest of the rules. This avoids 'auto' margins
   being negative on the start edge.

  C.2.63 Section 10.3.4 Block-level, replaced elements in normal flow

   Applied changes to section 10.3.2 and section 10.3.3 to block-level
   replaced elements in normal flow by referring to the calculations in
   those sections.

  C.2.64 Section 10.3.5 Floating, non-replaced elements

   Defined computations for 'auto' width floats as shrink-to-fit. (Floats
   were previously required to have fixed widths.)

  C.2.65 Section 10.3.6 Floating, replaced elements

   Applied changes to section 10.3.2 to this section by referencing it for
   'auto' width calculations.

  C.2.66 Section 10.3.7 Absolutely positioned, non-replaced elements

   Defined the static position of an element more precisely.

   Rewrote constraint rules.

   The 'direction' property of the containing block of the static position
   determines which side is clamped to the static position, not the
   'direction' property of the containing block of the absolutely
   positioned element.

  C.2.67 Section 10.3.8 Absolutely positioned, replaced elements

   In rule 1, applied sizing rules from section 10.3.2.

   In rule 2 (formerly rules 2 and 3), referred to new definition of
   'static position' in section 10.3.7.

   Also in rule 2, the 'direction' property of the containing block of the
   static position determines which side is clamped to the static
   position, not the 'direction' property of the containing block of the
   absolutely positioned element.

   In rule 4 (formerly rule 5), prevented 'auto' left and right margins in
   resulting in a negative margin on the start edge.

  C.2.68 Section 10.4 Minimum and maximum widths

   Specified that if the containing block's width is negative, the used
   value of a percentage min/max width is zero.

   Specified that if the min/max width is specified in percentages and the
   containing block's width depends on this element's width, then the
   resulting layout is undefined in CSS 2.1.

   The UA is no longer allowed to select an arbitrary minimum width.

   The used width of replaced elements with an intrinsic ratio and both
   'width' and 'height' specified as 'auto' is now calculated according to
   a table designed to preserve the intrinsic ratio as much as possible
   within the given constraints.

  C.2.69 Section 10.5 Content height

   Removed mention of 'line-height' for inline elements since their
   content box height no longer depends on 'line-height'.

   Percentage heights on absolutely-positioned elements are no longer
   treated as 'auto' when the containing block's height is not explicitly
   specified. Added a note to explain why this is possible.

   Specified that a percentage height on the root element is relative to
   the initial containing block.

  C.2.70 Section 10.6 Calculating heights and margins

   The computed values of 'top' and 'bottom' for are now defined in
   section 9.3.2. The value 'auto' does not always compute to zero.

   Added section 10.6.6 to cover cases that are no longer covered under
   the previous sections.

   Added section 10.6.7 to define 'auto' heights for block formatting
   context roots. (Unlike other block boxes, the height of these boxes
   increases to accommodate any normal-flow descendant floats.)

  C.2.71 Section 10.6.1 Inline, non-replaced elements

   The height of an inline box is no longer given by the 'line-height'
   property and is now undefined. This section now suggests that the
   height of the box can be based on the font.

  C.2.72 Section 10.6.2 Inline replaced elements, block-level replaced elements
  in normal flow, 'inline-block' replaced elements in normal flow and floating
  replaced elements

   The sizing algorithm for replaced elements now takes into account and
   attempts to preserve the replaced content's intrinsic ratio. Sizing of
   replaced elements with percentage intrinsic sizes and without intrinsic
   sizes is now also defined.

   Specified that for inline elements, the margin box is used when
   calculating the height of the line box.

  C.2.73 Section 10.6.3 Block-level non-replaced elements in normal flow when
  'overflow' computes to 'visible'

   This section now only applies to elements whose 'overflow' value
   computes to 'visible'; elements with other values of 'overflow' are
   discussed in the new section 10.6.7 ('Auto' heights for block
   formatting context roots).

  C.2.74 Section 10.6.4 Absolutely positioned, non-replaced elements

   Defined the static position of an element more precisely.

   Rewrote constraint rules.

  C.2.75 Section 10.6.5 Absolutely positioned, replaced elements

   In rule 1, applied sizing rules from section 10.6.2.

  C.2.76 Section 10.7 Minimum and maximum heights

   Percentage min/max heights on absolutely-positioned elements are no
   longer treated as '0'/'none' when the containing block's height is not
   explicitly specified. However if the containing block's width depends
   on an element's percentage width, then the resulting layout is
   undefined in CSS 2.1.

   The used width of replaced elements with an intrinsic ratio and both
   'width' and 'height' specified as 'auto' is now calculated according to
   a table designed to preserve the intrinsic ratio as much as possible
   within the given constraints.

  C.2.77 Section 10.8 Line height calculations

   Added rule 4 to specify that the height of the line box must be at
   least as much as that specified by the 'line-height' property on the
   this block.

  C.2.78 Section 10.8.1 Leading and half-leading

   UAs are no longer permitted to clip content to the line box, and are
   instead asked to render overlapping boxes in document order.

   'line-height' set on a block no longer specifies the minimal height of
   each inline box; instead it specifies the minimal height of each line
   box. The exact effect of this requirement is expressed in terms of
   struts; it is affected by vertical-alignment.

   Adjusted text to reflect that the content box height of an inline is no
   longer dictated by the 'line-height' property.

   Since the content box is now defined by the font and not by the
   line-height, 'text-top' and 'text-bottom' refer to the content area
   instead of the font.

   Defined 'top' and 'bottom' alignment in terms of aligned subtrees to
   take into account any protruding descendants.

   Defined the baseline of inline tables and inline blocks.

  C.2.79 Section 11.1 Overflow and clipping

   Specified that 'overflow' clips to the padding edge.

  C.2.80 Section 11.1.1 Overflow

   'projection' media are no longer permitted to print overflowing content
   for 'overflow: scroll'. 'Print' media now may, as opposed to should.

   UAs are now required to apply the 'overflow' property set on the root
   element to the viewport. Additionally, HTML UAs must use the 'overflow'
   property on the HTML BODY element instead if the root element's
   'overflow' value is 'visible'.

   Specified placement of scrollbar in the box model.

   The width of any scrollbars is no longer included in the width of the
   containing block. (And consequently, all text in section 10.3 that
   subtracts the scrollbar width from the containing block width has been
   removed.)

  C.2.81 Section 11.1.2 Clipping: the 'clip' property

   The 'clip' property now applies only to absolutely positioned elements.
   Furthermore, it applies to those elements even when their 'overflow' is
   'visible'.

   The default value of 'clip', 'auto', now indicates no clipping rather
   than clipping to the element's border box.

   Values of "rect()" should be separated by commas. UAs are required to
   support this syntax, but may also support a space-separated syntax
   since CSS2 was not clear about this.

   While CSS2 specified that values of "rect()" give offsets from the
   respective sides of the box, current implementations interpret values
   with respect to the top and left edges for all four values (top, right,
   bottom, and left). This is now the specified interpretation.

  C.2.82 Section 11.2 Visibility

   The 'visibility' property is now defined to inherit, and descendant
   elements can override an ancestor's hidden visibility.

  C.2.83 Chapter 12 Generated content, automatic numbering, and lists

   Moved all discussion of aural rendering to Appendix A.

  C.2.84 Section 12.1 The :before and :after pseudo-elements

   Removed restrictions on which properties and property values are
   allowed on ':before' and ':after' pseudo-elements.

  C.2.85 Section 12.2 The 'content' property

   The initial value of 'content' is now 'normal', not the empty string.

   The 'content' property now distinguishes between the empty string,
   which creates an empty box; and 'normal'/'none', which create no box at
   all. (There is no distinction between 'normal' and 'none' in level 2.)

   A UA is now allowed to report a URI that fails to download.

   Removed recommendation to authors to put rules with media-sensitive
   'content' properties inside '@media'.

   Whether '\A' escapes in generated content create line breaks is now
   subject to the 'white-space' property.

   The former section 12.3 on interaction between ':before', ':after' and
   elements with 'display: compact' or 'display: run-in' has been removed.
   (The interaction is already fully defined, because generated content
   consists of boxes in the tree, no different from other boxes.)

  C.2.86 Section 12.3.2 Inserting quotes with the 'content' property

   Specified that extra 'close-quote's and 'no-close-quote's (those
   without a matching 'open-quote' or 'no-open-quote') are not rendered,
   and that neither 'close-quote' nor 'no-close-quote' cause the quoting
   depth to be negative.

  C.2.87 Section 12.4 Automatic counters and numbering

   Defined what a rule with duplicate counters, such as 'counter-reset:
   section 2 section', means.

  C.2.88 Section 12.4.1 Nested counters and scope

   The scope of a counter no longer defaults to the whole document, but
   starts at the first element that uses the counter. (This affects
   counters that are used without a prior 'counter-reset' to set the scope
   explicitly.)

  C.2.89 Section 12.5 Lists

   Removed text in section 12.5 (formerly 12.6) relating to the 'marker'
   display value.

   Removed the 'marker-offset' property (and thus former section 12.6.1).

  C.2.90 Section 12.5.1 Lists

   The list styles 'hebrew', 'armenian', 'georgian', 'cjk-ideographic',
   'hiragana', 'katakana', 'hiragana-iroha' and 'katakana-iroha' have been
   removed due to lack of implementation experience. (They are expected to
   return in the CSS3 Lists module.)

   Removed the sentence that said that an unknown value for
   'list-style-type' should cause the value 'decimal' to be used instead.
   Instead, normal parsing rules apply and cause the rule to be ignored.

   The size of list style markers without an intrinsic size is now
   defined.

  C.2.91 Chapter 13 Paged media

   The 'size', 'marks', and 'page' properties are not part of CSS 2.1.

  C.2.92 Section 13.2.2 Page selectors

   The requirement for UA's to honor different declarations for :left,
   :right, and :first pages has been softened to simplify implementations:
   the page area of the :first page may be used for :left and :right pages
   as well.

  C.2.93 Section 13.3.1 Page break properties

   UAs are now only required to apply the page break properties to
   block-level elements in the normal flow of the root element, not to
   other blocks.However, UAs are now permitted to apply these properties
   to elements other than block-level elements.

   Defined treatment of margins, borders, and padding when a page break
   splits a box.

   The 'page-break-inside' property no longer inherits.

  C.2.94 Section 13.3.3 Allowed page breaks

   The 'page-break-inside' property of all ancestors is checked for
   page-breaking restrictions, not just that of the breakpoint's parent.

   When dropping restrictions to find a page breaking opportunity, rule A
   is dropped together with B and D rather than together with C.

   Removed restriction on breaking within absolutely positioned boxes.

  C.2.95 Section 14.2.1 Background properties

   For 'background-position', the restriction that keywords cannot be
   combined with percentage or length values is removed. I.e., a value
   like: '25% top' is now allowed. Also, 'background-position' now applies
   to all elements, not just to block-level and replaced elements.

   User agents are no longer allowed to treat a value of 'fixed' for
   'background-attachment' as 'scroll'. Instead they must ignore all such
   declarations as if 'fixed' were an invalid value.

   The size of background images without an intrinsic size is now defined.

  C.2.96 Section 14.3 Gamma correction

   The contents of this section is now a non-normative note.

  C.2.97 Chapter 15 Fonts

   The 'font-stretch' and 'font-size-adjust' properties have been removed
   in CSS 2.1.

   Font descriptors, the '@font-face' declaration, and all associated
   parts of the font matching algorithm have been removed in CSS 2.1.

  C.2.98 Section 15.2 Font matching algorithm

   In this section (previously 15.5), in step 5 (previously 8) of the font
   matching algorithm, the UA is now allowed to use multiple default
   fallback fonts to find a glyph for a given character.

   In the per-property rule 2, specified that if there is only a
   small-caps font in a given family, then that font will be selected by
   'normal'.

  C.2.99 Section 15.2.2 Font family

   The "missing character" glyph is no longer considered a match for the
   last font in a font set, but is now considered a match for U+FFFD.

   Certain punctuation characters when appearing in unquoted font family
   names are now required to be escaped.

  C.2.100 Section 15.5 Small-caps

   The 'font-variant' property's effect is no longer restricted to
   bicameral scripts.

  C.2.101 Section 15.6 Font boldness

   The computed value of 'font-weight' has been defined more precisely
   such that the 'bolder' and 'lighter' values have an appropriate effect
   when inheriting through elements with different font-families.

  C.2.102 Section 15.7 Font size

   Removed suggestion of 1.2 fixed ratio between keyword font sizes in
   favor of notes recommending a variable ratio and a smallest font-size
   no less than 9 pixels per EM unit.

   Added table mapping CSS font-size keywords to HTML font size numbers.

  C.2.103 Chapter 16 Text

   The 'text-shadow' property is not in CSS 2.1.

  C.2.104 Section 16.2 Alignment

   The initial value of 'text-align' is no longer UA-defined but a
   nameless value that acts as 'left' if 'direction' is 'ltr', 'right' if
   'direction' is 'rtl'.

   The <string> value for 'text-align' is not part of CSS 2.1.

   For 'text-align', specified that 'justify' is treated as the initial
   value when computed value of 'white-space' is 'pre' or 'pre-line'.

  C.2.105 Section 16.3.1 Underlining, over lining, striking, and blinking

   More precisely defined what boxes are affected by text decorations
   specified on a given element.

   Specified that underlines, overlines, and line-throughs apply only to
   text.

   Specified that an underline, overline, or line-through applied across a
   line must be at a constant vertical position and with a constant
   thickness across the entire line.

   Specified how text decorations are affected by relative positioning on
   descendants.

   User agents are now allowed to recognize the 'blink' value but not
   blink, whereas before they were required to ignore the 'blink' value if
   they chose not to support blinking text.

   Added text to allow older UAs to conform to this section if they follow
   CSS2's 'text-decoration' requirements but not the additional
   requirements in CSS2.1.

  C.2.106 Section 16.4 Letter and word spacing

   Support for the various values of 'letter-spacing' and 'word-spacing'
   is no longer optional.

   Specified that word spacing affects each space, non-breaking space, and
   ideographic space left in the text after white space processing rules
   have been applied.

  C.2.107 Section 16.5 Capitalization

   UAs are no longer allowed to not transform characters for which there
   is an appropriate transformation but which are outside of Latin-1.

  C.2.108 Section 16.6 White space

   The 'white-space' property now applies to all elements, not just to
   block-level elements.

   "\A" in generated content no longer forces a break for 'normal' and
   'nowrap' values of 'white-space'.

   Specified that the CSS white space processing model assumes all
   newlines have been normalized to line feeds.

   Added section 16.6.1 to precisely define white space handling.

   Added section 16.6.3 to specify handling of control and combining
   characters.

  C.2.109 Chapter 17 Tables

   Moved all discussion of aural rendering and related properties to
   Appendix A.

   Updated prose to use the terms "specified", "computed" and "used" as
   appropriate when referencing values. (See changes to section 6.1.)

  C.2.110 Section 17.2 The CSS table model

   Defined handling of multiple 'table-header-group' and
   'table-footer-group' elements.

   UAs are no longer allowed to ignore the table display values on
   arbitrary HTML elements, only on HTML table elements.

  C.2.111 Section 17.2.1 Anonymous table objects

   Changed rules so that internal table elements without an enclosing
   'table' or 'inline-table' box generate an anonymous 'inline-table'
   rather than an anonymous 'table' when inside a "display: inline" parent
   element.

   The anonymous table object rules now treat anonymous boxes as equal to
   elements' boxes. Replaced several instances of the term "element" with
   "box", removed several instances of "(in the document tree)" and
   clarified that anonymous boxes generated in earlier rules are part of
   the input to later rules. Also replaced the term "object" with "box",
   as is used throughout the rest of the specification.

   HTML UAs are no longer exempt from the anonymous box generation rules.

  C.2.112 Section 17.4 Tables in the visual formatting model

   The relationship of the caption box, table box, and outer anonymous
   table box has been changed as follows:
     * The margins of the table box now apply to the outer (anonymous)
       table box that encloses both the table box and the caption(s), not
       to the inner table box.
     * The width of the anonymous box is now equal to the border-box width
       of the table box inside it instead of adapting to the widths and
       positions of both the table box and its captions.

  C.2.113 Section 17.4.1 Caption position and alignment

   The 'left' and 'right' values on 'caption-side' have been removed.

  C.2.114 Section 17.5 Visual layout of table contents

   Changed rule 5 in grid layout rules to allow overlapping of table cells
   instead of leaving skipping a gap in the grid to avoid overlap.

  C.2.115 Section 17.5.1 Table layers and transparency

   In point 6, changed 'These "empty" cells are transparent' to:

     If the value of their 'empty-cells' property is 'hide' these "empty"
     cells are transparent through the cell, row, row group, column, and
     column group backgrounds, letting the table background show through.

  C.2.116 Section 17.5.2.1 Fixed table layout

   Specified that in fixed table layout, extra columns in rows after the
   first must not be rendered.

  C.2.117 Section 17.5.2.2 Automatic table layout

   Restricted inputs to the table layout algorithm for 'table-layout:
   auto', whether or not the algorithm described in this section is used,
   to the width of the containing block and the content of, and any CSS
   properties set on, the table and any of its descendants.

   Added rule 4 to include the column group's width in the algorithm for
   determining column widths.

  C.2.118 Section 17.5.3 Table height algorithms

   The 'height' property on tables is now treated as a minimum height; the
   UA no longer has the option of using 'height' to constrain the size of
   the table to be smaller than its contents.

   The baseline of a cell is now defined much more precisely.

   Defined the baseline of a row with no baseline-aligned cells.

  C.2.119 Section 17.5.4 Horizontal alignment in a column

   The <string> value for 'text-align' is not part of CSS 2.1.

  C.2.120 Section 17.6 Borders

   Several popular browsers assume an initial value for 'border-collapse'
   of 'separate' rather than 'collapse' or exhibit behavior that is close
   to that value, even if they do not actually implement the CSS table
   model. 'Separate' is now the initial value.

  C.2.121 Section 17.6.1 The separated borders model

   Specified the effect of padding on the table element.

   Specified which parts of the table are included in the width
   measurement.

  C.2.122 Section 17.6.1.1 Borders and Backgrounds around empty cells

   Refined definition of "empty" when used as a condition for the
   'empty-cells' property so that it is not triggered when the cell
   includes any child elements, even if they are empty.

   The 'empty-cells' property now hides both borders and backgrounds, not
   just borders.

   Changed behavior of a row when it collapses due to 'empty-cells': it is
   no longer treated as "display: none". Instead it is given zero height
   and its associated border-spacing is eliminated.

  C.2.123 Section 17.6.2 The collapsing border model

   The outer half of the table borders no longer lie in the margin area.
   Specified which part of the table is considered the border are in the
   collapsed borders model and how its width is calculated. The edges of
   the box in which the table background is painted is, however left
   explicitly undefined.

  C.2.124 Section 17.6.2.1 Border conflict resolution

   Defined in rule 4 what happens when two elements of the same type
   conflict and their borders have the same width and style.

  C.2.125 Section 18.1 Cursors: the 'cursor' property

   The size of cursors without an intrinsic size is now defined.

  C.2.126 Section 18.4 Dynamic outlines

   Position of outline with respect to the border edge is now only
   suggested, not required.

   Conformant UAs are now allowed to ignore the 'invert' value. In such
   UAs the initial value of 'outline-color' is the value of the 'color'
   property.

  C.2.127 Chapter 12 Generated content, automatic numbering, and lists

   The 'marker' value for 'display' does not exist in CSS 2.1

  C.2.128 Appendix A. Aural style sheets

   Chapter 19 on aural style sheets has become appendix A and is not
   normative in CSS 2.1. Related units (deg, grad, rad, ms, s, Hz, kHz)
   are also moved to this appendix, as is the 'speak-header' property from
   the "tables" chapter and other notes on aural table rendering. The
   'aural' media type is deprecated in favor of the new 'speech' media
   type.

  C.2.129 Appendix A Section 5 Pause properties

   Changed the initial value of 'pause-before' and 'pause-after' to be 0
   instead of UA-defined.

   A note has been added to this section (formerly 19.4) about the change
   in position and behavior of pauses in CSS3 Speech compared to this
   appendix.

  C.2.130 Appendix A Section 6 Cue properties

   This section (formerly Section 19.5) now specifies the placement of
   cues and pauses with respect to the :before and :after pseudo-elements.

  C.2.131 Appendix A Section 7 Mixing properties

   The keywords 'mix' and 'repeat' may now appear in either order.

  C.2.132 Appendix B Bibliography

   Various references in Appendix B (formerly Appendix E) have been
   updated as appropriate.

   Switched [CSS1] from Normative to Informative.

   Updated URI reference from [RFC1808] and the
   draft-fielding-uri-syntax-01.txt to [RFC3986].

   Updated HTTP reference from [RFC2068] to [RFC2616].

   Removed normative references to [IANA] and [ICC32].

   Added normative references to [ICC42], [RFC3986], [RFC2070], [UAAG10].

   Added informative references to CSS2, CSS3 Color, CSS3 Lists,
   Selectors, CSS3 Speech, DOM 3 Core, MathML 2, P3P, RFC1630, SVG 1.1,
   XHTML 1, XML ID, and XML Namespaces.

   Removed informative references to [ISO10179] (DSSSL), [INFINIFONT],
   [ISO9899] (C), [MONOTYPE], [NEGOT], [OPENTYPE], [PANOSE], [PANOSE2],
   [POSTSCRIPT], [RFC1866] (HTML 2), [RFC1942] (HTML Tables),
   [TRUETYPEGX], [W3CStyle].

   Updated language tags references from [RFC1766] to [BCP47].

  C.2.133 Other

   The former informative appendix C, "Implementation and performance
   notes for fonts," is left out of CSS 2.1.

C.3 Errors

  C.3.1 Shorthand properties

   Shorthand properties take a list of subproperty values or the value
   'inherit'. One cannot mix 'inherit' with other subproperty values as it
   would not be possible to specify the subproperty to which 'inherit'
   applied. The definitions of a number of shorthand properties did not
   enforce this rule: 'border-top', 'border-right', 'border-bottom',
   'border-left', 'border', 'background', 'font', 'list-style', 'cue', and
   'outline'.

  C.3.2 Applies to

   The "applies to" line of many property definitions has been made more
   accurate by excluding or including table display types where
   appropriate.

  C.3.3 Section 4.1.1 (and G2)

   DELIM should not have included single or double quote. Refer also to
   section 4.1.6 on strings, which must have matching single or double
   quotes around them.

   Removed "A-Z" from the "nmchar" token: as CSS is case insensitive
   anyway, it was redundant.

   Corrected "unicode" macro to treat CRLF as a single character.

   Corrected "block" production to allow white space between declarations.

   In the rule for "any" (in the core syntax), corrected "FUNCTION" to
   "FUNCTION any* ')'".

  C.3.4 Section 4.1.3 Characters and case

   Corrected third paragraph to say that an '@import' rule can only be
   preceded by an '@charset' rule or other '@import' rules.

  C.3.5 Section 4.3 (Double sign problem)

   Several values described in subsections of this section incorrectly
   allowed two "+" or "-" signs at their beginnings.

  C.3.6 Section 4.3.2 Lengths

   Fixed double sign error in definition of <length>. (<number> already
   has a sign.)

   Corrected the suggested reference pixel to be based on a [INS: 96 dpi
   :INS] device, not 90 dpi. The visual angle is thus about [INS: 0.0213
   degrees :INS] instead of 0.0227, and a pixel at arm's length is about
   [INS: 0.26 mm :INS] instead of 0.28

   Corrected last sentence to refer to a unsupported used length, not an
   unsupported specified length.

  C.3.7 Section 4.3.3 Percentages

   Fixed double sign error in definition of <percentage>. (<number>
   already has a sign.)

  C.3.8 Section 4.3.4 URLs and URIs

   Defined escaping requirements in terms of the URI token so that no
   escaping requirements are missing from the prose.

   Included invalid URIs in last paragraph about URI error handling.

  C.3.9 Section 4.3.5 Counters

   Corrected syntax of counter() and counters() notation to allow white
   space between tokens.

  C.3.10 Section 4.3.6 Colors

   Deleted the comments about range restriction after the following
   examples:
em { color: rgb(255,0,0) }
em { color: rgb(100%, 0%, 0%) }

  C.3.11 Section 4.3.7 Strings

   (Formerly section 4.3.10) Corrected text to allow all forms of Unicode
   escapes for U+000A, not just the "\A" form, for including newlines in
   strings.

  C.3.12 Section 5.10 Pseudo-elements and pseudo-classes

   In the second bullet, added that the ':lang()' pseudo-class can also be
   deduced from the document in some cases.

  C.3.13 Section 6.4 The cascade

   Removed paragraph about imported style sheets being overridden by rules
   in the importing style sheet: imported style rules follow the cascade
   as specified in 6.4.1 Cascading order, exactly as if they were inserted
   in place of the @import rule.

  C.3.14 Section 8.1 Box Dimensions

   The definition of "content edge" has been changed to depend on 'width'
   and 'height' rather than directly on 'rendered content'.

   From the definition of "padding edge", deleted the sentence "The
   padding edge of a box defines the edges of the containing block
   established by the box." For information about containing blocks,
   consult Section 10.1.

  C.3.15 Section 8.2 Example of margins, padding, and borders

   The colors in the example HTML did not match the colors in the image.

  C.3.16 Section 8.5.4 Border shorthand properties

   Changed various border shorthands' syntax definitions to use the
   <border-width>, <border-style> and <'border-top-color'> value types as
   appropriate.

  C.3.17 Section 9.2.1 Block-level elements and block boxes

   Excepted table elements from second paragraph about principal block
   boxes and their contents.

   Corrected sentence to say "either only block boxes or only inline
   boxes" instead of "only block boxes".

  C.3.18 Section 9.3.1 Choosing a positioning scheme

   In the definition of "position: static", added 'right' and 'bottom' to
   the sentence saying that 'top' and 'left' do not apply.

  C.3.19 Section 9.3.2 Box offsets

   The properties 'top', 'right', 'bottom', and 'left', incorrectly
   referred to offsets with respect to a box's content edge. The proper
   edge is the margin edge. Thus, for 'top', the description now reads:
   "This property specifies how far a box's top margin edge is offset
   below the top edge of the box's containing block."

   Corrected text under property definitions to say that for
   relatively-positioned elements, 'top', 'right', 'bottom', and 'left'
   define the offset from the box's position in the normal flow, not from
   the edges of the containing block. (The previous definition conflicted
   with that was further down; since that text is now redundant, it has
   been removed.)

  C.3.20 Section 9.4.1 Block formatting contexts

   In paragraph about relationship of a box's outer edges to its
   containing block's edges, corrected parenthetical to say that line
   boxes, not the content area, may shrink due to floats.

  C.3.21 Section 9.4.2 Inline formatting context

   Added "and the presence of floats" to "The width of a line box is
   determined by a containing block".

  C.3.22 Section 9.4.3 Relative positioning

   In the first paragraph, added "or floated" to the phrase "laid out
   according to the normal flow" as floated elements can be relatively
   positioned but are not part of the normal flow.

  C.3.23 Section 9.5 Floats

   Corrected sentence about not enough horizontal room for the float to
   say that it is shifted downward until either it fits or there are no
   more floats present.

  C.3.24 Section 9.5.1 Positioning the float

   Correct "Applies to" line and prose to say that the 'float' property
   can be set for any element but only applies to elements that are not
   absolutely positioned.

  C.3.25 Section 9.5.2 Controlling flow next to floats

   Removed sentence saying that 'clear' may only be specified for
   block-level elements: it can be specified for any element, it only
   applies to block-level elements.

  C.3.26 Section 9.6 Absolute positioning

   Corrected sentence that said absolutely positioned boxes establish a
   new containing block for absolutely positioned descendants to except
   fixed positioned descendants.

  C.3.27 Section 9.7 Relationships between 'display', 'position', and 'float'

   In rule 1, corrected "user agents must ignore 'position' and 'float" to
   "'position' and 'float' do not apply".

  C.3.28 Section 9.10 Text direction

   Corrected note about 'direction' on table column elements to say that
   "columns are not the ancestors of the cells in the document tree"
   rather than saying "columns do not exist in the document tree".

   Added table cells, table captions, and inline blocks alongside
   block-level elements in description of 'bidi-override' value. Also
   corrected the prose to handle anonymous child blocks.

   Updated mention of Unicode's embedding limit from 15 to 61.

  C.3.29 Section 10.1 Definition of "containing block"

   Included table cells (and inline blocks) together with block-level
   elements in rule 2 defining the containing block of
   non-absolutely-positioned elements.

  C.3.30 Section 10.3.3 Block-level, non-replaced elements in normal flow

   In the last sentence of the paragraph following the equation ("If the
   value of 'direction' is 'ltr', this happens to 'margin-left' instead")
   substituted 'rtl' for 'ltr'.

  C.3.31 Section 10.4 Minimum and maximum widths

   The initial value for 'min-width' is now '0' rather than UA-dependent.

   Corrected "applies to" exception for both 'min-width' and 'max-width'
   from "table elements" to "table rows and row groups".

   Specified that negative values for 'min-width' and 'max-width' are
   illegal.

  C.3.32 Section 10.6.3 Block-level non-replaced elements in normal flow when
  'overflow' computes to 'visible'

   Added that 'auto' height also depends on whether the element has
   padding or borders, as these influence margin-collapsing behavior.

   Added text to correctly account for margin collapsing behavior.

  C.3.33 Section 10.7 Minimum and maximum heights

   Corrected "applies to" exception for both 'min-width' and 'max-width'
   from "table elements" to "table columns and column groups".

   Specified that negative values for 'min-height' and 'max-height' are
   illegal.

  C.3.34 Section 11.1.1 Overflow

   Corrected "applies to" line for 'overflow' from "block-level and
   replaced elements" to "non-replaced block-level elements, table cells,
   and inline-block elements".

   The example of a DIV element containing a BLOCKQUOTE containing another
   DIV was not rendered correctly. The first style rule applied to both
   DIVs, so the second DIV box should have been rendered with a red border
   as well. The second DIV has now been changed to a CITE, which does not
   have a red border.

  C.3.35 Section 11.1.2 Clipping: the 'clip' property

   Corrected "rect (<top> <right> <bottom> <left>)" to "rect(<top>,
   <right>, <bottom>, <left>)".

  C.3.36 Section 11.2 Visibility

   Corrected initial value of 'visibility' to 'visible'.

  C.3.37 Section 12.4.2 Counter styles

   The example used the style 'hebrew', which does not exist in CSS
   level 2. Changed to 'lower-greek'.

  C.3.38 Section 12.6.2 Lists

   Under the 'list-style' property, the example:
ul > ul { list-style: circle outside } /* Any UL child of a UL */

   could never match valid HTML markup (since a UL element cannot be a
   child of another UL element). An LI has been inserted in between.

  C.3.39 Section 14.2 The background

   Second sentence: "In terms of the box model, 'background' refers to the
   background of the content and the padding areas" now also mentions the
   border area. (See also errata to section 8.1 above.) Thus:

     In terms of the box model, "background" refers to the background of
     the content, padding and border areas.

  C.3.40 Section 14.2.1 Background properties

   Under 'background-image', defined the image tile size used when the
   background image has intrinsic sizes specified in percentages or no
   intrinsic size.

   Under 'background-repeat', the sentence "All tiling covers the content
   and padding areas [...]" has been corrected to

     "All tiling covers the content, padding [INS: and border :INS] areas
     [...]".

   Under 'background-attachment', the value 'scroll' is defined to scroll
   with the "containing block" rather than with the "document". Also the
   sentence "Even if the image is fixed [...] background or padding area
   of the element" has been corrected to

     Even if the image is fixed, it is still only visible when it is in
     the background, padding [INS: or border :INS] area of the element.

  C.3.41 Section 15.2 Font matching algorithm

   In bullet 2, changed "the UA uses the 'font-family' descriptor" to "the
   UA uses the 'font-family' property".

  C.3.42 Section 15.7 Font size

   The statement "Negative values are not allowed" for 'font-size' now
   applies to percentages as well as lengths.

  C.3.43 Section 16.1 Indentation

   Corrected 'text-indent' to apply to table cells (and inline blocks) as
   well as block-level elements.

  C.3.44 Section 16.2 Alignment

   Corrected 'text-align' to apply to table cells (and inline blocks) as
   well as block-level elements.

   Changed prose about the effect of 'justify' to be less correct.

   Corrected the note to say that justification is also dependent on the
   script, not just the language, of the text.

  C.3.45 Section 17.2 The CSS table model

   In the definition of table-header-group, changed "footer" to "header"
   in "Print user agents may repeat footer rows on each page spanned by a
   table."

  C.3.46 Section 17.2.1 Anonymous table objects

   Added 'table-header-group' and 'table-footer-group' alongside mentions
   of 'table-row-group' where missing.

   Corrected 'caption' to 'table-caption'.

   Added missing rule (#3) for 'table-column' boxes.

   Added 'table-caption' and 'table-column-group' to list of boxes
   requiring a 'table' or 'inline-table' parent in rule 4.

   Added rules 5 and 6 to generate 'table-row' boxes where necessary for
   children of 'table'/'inline-table' and
   'table-row-group'/'table-header-group'/'table-footer-group' boxes.

  C.3.47 Section 17.4 Tables in the visual formatting model

   Specified handling of multiple caption boxes.

   Specified that the anonymous outer table box is a 'block' box if the
   table is block-level and an 'inline-block' box if the table is
   inline-level but that the anonymous outer table box cannot accept
   run-ins.

  C.3.48 Section 17.5 Visual layout of table contents

   Correct text that said all internal table elements have padding; change
   to say that of these only table cells have padding.

   The following note:

     Note. Table cells may be relatively and absolutely positioned, but
     this is not recommended: positioning and floating remove a box from
     the flow, affecting table alignment.

   has been amended as follows:

     Note. Table cells may be positioned, but this is not recommended:
     absolute and fixed positioning, as well as floating, remove a box
     from the flow, affecting table size.

  C.3.49 Section 17.5.1 Table layers and transparency

   The rows and columns only cover the whole table in the collapsed
   borders model, not in the separated borders model.

   The points 2, 3, 4 and 5 have been corrected to define the area covered
   by rows, columns, row groups and column groups and thus the positioning
   and painting of backgrounds on those elements.

   Specify the handling of "missing cells".

  C.3.50 Section 17.6.1 The separated borders model

   In the image, changed "cell-spacing" to "border-spacing".

  C.3.51 Section 18.2 System Colors

   For the 'ButtonHighlight' value, changed the description from "Dark
   shadow" to "Highlight color".

  C.3.52 Section E.2 Painting order

   Changed "but any descendants which actually create a new stacking
   context" to "but any [INS: positioned descendants and :INS] descendants
   which actually create a new stacking context" (3 times).

   This change also occurred once in section 9.5 (Floats) and once in
   section section 9.9 (Layered presentation).

C.4 Clarifications

  C.4.1 Section 2.1 A brief CSS 2.1 tutorial for HTML

   This section has been marked non-normative.

  C.4.2 Section 2.2 A brief CSS 2.1 tutorial for XML

   This section has been marked non-normative.

   Added a statement about case-sensitivity of selectors for XML.

   The specification for the XML style sheet PI was written after CSS2 was
   finalized. The first line of the full XML example should not have been
   be <?XML:stylesheet type="text/css" href="bach.css"?>, but
<?xml-stylesheet type="text/css" href="bach.css"?>

  C.4.3 Section 2.3 The CSS 2.1 processing model

   This section has been marked non-normative.

  C.4.4 Section 3.1 Definitions

   Added a note to clarify that the deprecated/non-deprecated status of a
   feature is distinct from its normative/non-normative status.

   Under 'document language' clarified that CSS only describes the
   presentation of a document language, and has no effect on its
   semantics.

   Changed definition of 'replaced element' to "an element whose content
   is outside the scope of the CSS formatting model" and added further
   clarifying text. This clarifies that e.g., SVG images embedded in an
   XML document are also considered replaced elements, not just those
   linked in from an outside file. Also changed definition of 'rendered
   content' to be consistent with this clarification.

   Added under "Intrinsic dimension" that raster images without reliable
   resolution information are assumed to have a size of 1 px unit per
   image source pixel.

   Added definition for 'ignore'.

   Added definition for 'HTML user agent'.

   Added definition for 'property'.

  C.4.5 Section 4.1 Syntax

   Moved definitions of "immediately before" and "immediately after"
   forward so they apply to the whole Syntax section.

   Added sections 4.1.2.1 and 4.1.2.2 to defined vendor-specific
   extensions.

  C.4.6 Section 4.1.1 Tokenization

   Clarified that input that cannot be parsed according to the core syntax
   is ignored according to the rules for handling parsing errors.

   Clarified that input that cannot be tokenized or parsed has no meaning
   in CSS2.1.

  C.4.7 Section 4.1.3 Characters and case

   Clarified that when a CRLF pair terminates an escape sequence, the pair
   is treated as a single white space character as corrected in the
   tokenization rules.

   Replaced "[a-z0-9]" by "[a-zA-Z0-9]" as an extra reminder that CSS
   identifiers are case-insensitive.

  C.4.8 Section 4.1.7 Rule sets, declaration blocks, and selectors

   Replaced the term "{}-block" with "declaration block".

  C.4.9 Section 4.2 Rules for handling parsing errors

   Clarified that all property:value combinations and @-keywords that do
   not contain an identifier beginning with dash or underscore are
   reserved by CSS for future use.

   Clarified that when something inside an at-rule is ignored because it
   is invalid, this does not make the entire at-rule invalid.

   Referenced section 4.1.7 for parsing invalid bits inside declaration
   blocks.

  C.4.10 Section 4.3.1 Integers and real numbers

   Clarified that '-0' is equivalent to '0' and is not a negative number.

  C.4.11 Section 4.3.2 Lengths

   Clarified that negative length values on properties that do not allow
   them cause the declaration to be ignored.

  C.4.12 Section 4.3.4 URLs and URIs

   Reduced unnecessary discussion of what a URI is.

  C.4.13 Section 5.1 Pattern matching

   Added note about terminology change ("simple selector") between CSS2
   and CSS3.

  C.4.14 Section 5.7 Adjacent sibling selectors

   Clarified that text nodes and comments do not affect whether a sibling
   selector matches.

  C.4.15 Section 5.8.1 Matching attributes and attribute values

   Clarified ~= and |= by using the definitions from the Selectors module.

  C.4.16 Section 5.8.2 Default attribute values in DTDs

   Clarified that rules about default attribute values are the same,
   whether the default is specified in a DTD or by other means.

  C.4.17 Section 5.9 ID selectors

   Added a note that it depends on the document format which attributes
   are ID attributes.

  C.4.18 Section 5.11.3 The dynamic pseudo-classes: :hover, :active, and :focus

   Clarified that CSS 2.1 does not define if the parent of an element that
   matches ':active' or ':hover' itself also matches ':active' or
   ':hover'.

   Added note that, in CSS1, ':active' only applies to links.

  C.4.19 Section 5.11.4 The language pseudo-class: :lang

   Added a note to show the differences between ':lang(xx)' and
   '[lang=xx]'.

  C.4.20 Section 5.12.2 The :first-letter pseudo-element

   Clarified that digits can also be first letter.

  C.4.21 Section 6.2 Inheritance

   Clarified that computed values are inherited (not specified values) and
   that they become the specified value on the inheritor.

   Removed discussion of "default" styles for a document.

  C.4.22 Section 6.2.1 The 'inherit' value

   Clarify that 'inherit' can be used on properties that are not normally
   inherited and that when set on the root element, it has the effect of
   assigning the property's initial value.

  C.4.23 Section 6.3 The @import rule

   Except @charset from the statement that @imports must precede all other
   rules.

  C.4.24 Section 6.4 The Cascade

   Obfuscated note about system settings and UA limitations.

  C.4.25 Section 6.4.1 Cascading order

   Various editorial changes to clarify sort order.

  C.4.26 Section 6.4.3 Calculating a selector's specificity

   Added a note:

     The specificity is based only on the form of the selector. In
     particular, a selector of the form "[id=p33]" is counted as an
     attribute selector (a=0, b=1, c=0), even if the id attribute is
     defined as an "ID" in the source document's DTD.

  C.4.27 Section 7.2.1 The @media rule

   Clarify that Style rules outside of @media rules apply to the same
   media types that the style sheet itself applies to.

  C.4.28 Section 7.3 Recognized media types

   Added text to clarify that media types are mutually exclusive, but a UA
   can render simultaneously to canvases with different media types.

  C.4.29 Section 7.3.1 Media groups

   Split "aural" media group into "audio" and "speech".

  C.4.30 Section 8.1 Box dimensions

     * The terms "content box", "padding box", "border box", and "margin
       box" have been defined.
     * Border backgrounds are not specified by border properties. Changed
       the last paragraph of 8.1 to:

     The background style of the content, padding, and border areas of a
     box is specified by the 'background' property of the generating
     element. Margin backgrounds are always transparent.
     * Removed definition of "box width" and "height".

  C.4.31 Section 8.3 Margin properties

   Added a sentence to note that vertical margins have no effect on
   non-replaced inline elements.

  C.4.32 Section 8.3.1 Collapsing margins

   Changed "absolute maximum" to "maximum of the absolute values" in
   sentence about negative margins collapsing.

   Added this clarifying note to the first bullet of the explanation of
   vertical collapsing of margins:

     Note. Adjoining boxes may be generated by elements that are not
     related as siblings or ancestors.

   Emphasized that floating elements' margins do not collapse even between
   a float and its in-flow children.

   Emphasized that absolutely positioned elements' margins do not collapse
   even between the positioned element and its in-flow children.

  C.4.33 Section 8.5.3 Border style

   Changed description of 'none' value to not imply that all four border
   widths are set to zero.

  C.4.34 Section 9.1.1 The viewport

   Changed the sentence "When the viewport is smaller than the ..., the
   user agent should offer a scrolling mechanism" to use "area of the
   canvas on which the document is rendered" instead of "document's
   initial containing block".

  C.4.35 Section 9.2.4 The 'display' property

   Clarified that 'display: none' also applies to non-visual media.

  C.4.36 Section 9.3.1 Choosing a positioning scheme

   Clarified that the margins of fixed positioned boxes do not collapse
   with any other margins.

   Clarified that in print media fixed boxes are rendered on every page.

  C.4.37 Section 9.3.2 Box offsets

   Clarified that negative lengths and percentages are allowed as values
   of 'top', 'right', 'bottom', and 'left'.

   Added "For replaced elements, the effect of this value depends only on
   the intrinsic dimensions of the replaced content. See the sections on
   the width and height of absolutely positioned, replaced elements for
   details." to the definition of 'auto' because that's not what chapter
   10 says at all.

  C.4.38 Section 9.4.2 Inline formatting context

   Clarified that 'justify' stretches "spaces and words in inline boxes";
   previous text simply said that it stretches "inline boxes".

   The statement "When an inline box is split, margins, borders, and
   padding have no visual effect where the split occurs." has been
   generalized. Margins, borders, and padding have no visual effect where
   one or more splits occur.

   Clarified that an inline box that exceeds the width of a line box and
   cannot be split therefore overflows the line box.

   Removed sentence about formatting of margins, borders, and padding for
   split inline boxes not being fully defined when affected by bidi as
   that situation is now defined in section 8.6.

  C.4.39 Section 9.4.3 Relative positioning

   Clarified that although relative positioning normally does not directly
   affect layout, it may affect layout indirectly through the creation of
   scrollbars.

   Relatively positioned boxes do not always establish new containing
   blocks. Changed the second paragraph to refer to the section on
   containing blocks accordingly.

   The paragraph about dynamic movement and superscripting has been
   shifted into a non-normative note.

  C.4.40 Section 9.5 Floats

   Clarified that line boxes are shortened to make room for the margin box
   of the float.

   Added some text to clarify what "Any content in the current line before
   a floated box is reflowed in the first available line on the other side
   of the float" means.

   Clarified floats' position in the stacking order.

  C.4.41 Section 9.5.1 Positioning the float

   Clarified that the elements referenced in the float behavior rules are
   in the same block formatting context as the float.

  C.4.42 Section 9.5.2 Controlling flow next to floats

   Clarified that the effects of 'clear' do not consider floats in other
   block formatting contexts.

  C.4.43 Section 9.8 Comparison of normal flow, floats, and absolute positioning

   Added a note to clarify that the images in this section are not drawn
   to scale and are illustrations, not reference renderings.

  C.4.44 Section 10.1 Definition of "containing block"

   Noted that a containing block formed by inline elements may wind up
   with a negative containing block width.

  C.4.45 Section 10.2 Content width

   In the definition of <length> values for the 'width' property, changed
   "Specifies a fixed width" to "Specifies the width of the content area
   using a length unit".

  C.4.46 Section 10.3.3 Block-level, non-replaced elements in normal flow

   Clarified that setting both left and right margins to 'auto'
   horizontally centers the element within its containing block.

  C.4.47 Section 10.3.8 Absolutely positioning, replaced elements

   Clarified which part of the text of section 10.3.7 is re-used.

  C.4.48 Section 10.4 Minimum and maximum widths

   Clarified that 'min-width' and 'max-width' do not affect the computed
   values of any properties. (They only affect the used value.)

  C.4.49 Section 10.6 Calculating heights and margins

   Clarified that these rules apply to the root element just as to any
   other element.

  C.4.50 Section 10.7 Minimum and maximum heights

   Clarified that 'min-width' and 'max-width' do not affect the computed
   values of any properties. (They only affect the used value.)

  C.4.51 Section 10.8 Line height calculations

   Removed clarifying note about line height being taller than tallest
   single inline box due to vertical alignment.

  C.4.52 Section 10.8.1 Leading and half-leading

   Removed "slightly" from the note "Values of this property have [DEL:
   slightly :DEL] different meanings in the context of tables."

  C.4.53 Section 11.1 Overflow and clipping

   Clarified when absolute positioning and negative margins cause
   overflow.

   Added 'text-indent' to the list of things that can cause overflow.

   Removed mention of 'clip' since it no longer affects most elements;
   mentioned that the 'overflow' property also specifies whether a
   scrolling mechanism is provided to access clipped content.

  C.4.54 Section 11.1.1 Overflow

   Clarified that descendant elements whose containing block is the
   viewport or an ancestor of the element are not affected by overflow
   clipping.

   Removed unnecessary mentions of the 'clip' property from the 'hidden'
   value definition.

  C.4.55 Section 11.1.2 Clipping

   Changed "portion of an element's rendered content" to "portion of an
   element's border box" since clipping also affects the element's
   backgrounds and borders.

   Clarified what parts of the element are affected by clipping.

   Clarified that clipped content does not cause overflow.

   Clarified that arguments of clip() can be separated by spaces or by
   commas, but not a combination.

  C.4.56 Section 11.2 Visibility

   Clarified that descendants of a 'visibility: hidden' element will be
   visible if they have 'visibility: visible'.

  C.4.57 Section 12.1 The :before and :after pseudo-elements

   Clarified that :before and :after pseudo-elements interact with other
   boxes as if they were real elements just inside their associated
   element.

   Noted that the interaction of :before and :after with replaced elements
   is left undefined for now.

  C.4.58 Section 12.2 The 'content' property

   Clarified which counters are used for counter() and counters() in case
   there are multiple counters of the same name.

  C.4.59 Section 12.3.2 Inserting quotes with the 'content' property

   Removed note about common typographic practices when quotes in
   different languages are mixed.

  C.4.60 Section 12.4 Automatic counters and numbering

   In the "self-nesting" behavior of counters, clarified that merely using
   a counter in a child element does not create a new instance of it: only
   resetting it does.

   Clarified that the scope of a counter does not include any elements in
   the scope of a counter with the same name created by a 'counter-reset'
   on a later sibling or a later 'counter-reset' on the same element.

   Removed sentence about scope of 'counter-increment' without prior
   'counter-reset' as that is now defined (differently) under "12.4.1
   Nested counters and scope."

  C.4.61 Section 12.4.3 Counters in elements with 'display: none'

   Clarified that pseudo-elements that generate no boxes also do not
   increment counters.

  C.4.62 Section 14.2 The background

   Clarified that the root background image, although painted over the
   entire canvas, is anchored as if painted only for the root element, and
   that the root's background is only painted once.

   Clarified rules for propagation of background settings on HTML's <body>
   element to the root.

   Added statement about z-index of backgrounds for elements that form a
   stacking context and referred to z-index property for details.

   Added this note after the first paragraph after
   'background-attachment':

     Note that there is only one viewport per document. I.e., even if an
     element has a scrolling mechanism (see 'overflow'), a 'fixed'
     background does not move with it.

   Definition of 'background-position' has been rewritten as normative
   rules rather than just examples.

   Stated that the tiling and positioning of background images for inline
   elements is undefined in CSS2.1.

  C.4.63 Section 15.1 Fonts Introduction

   Drastically shortened introduction.

  C.4.64 Section 15.2 Font matching algorithm

   In the per-property rule 2, clarified that 'normal' matches the
   non-small-caps variant (if there is one).

  C.4.65 Section 15.2.2 Font family

   Removed discussion of font-matching algorithm. (It is already covered
   in the font-matching algorithm's own section.

   Clarified that quoted strings that are the same as a keyword value must
   be treated as font family names and not as the keyword value (which
   must be unquoted).

  C.4.66 Section 15.3.1 Generic font families

   This section, previously section 15.2.6, has been moved but no other
   change was made.

  C.4.67 Section 15.4 Font styling

   The text for this section (formerly part of 15.2.3) has been reverted
   to its CSS1 format.

  C.4.68 Section 15.5 Small-caps

   The text for this section (formerly part of 15.2.3) has been reverted
   to its CSS1 format.

   Clarified that CSS2.1 cannot select font variants besides small-caps.

   Clarified that when "font-variant: small-caps" results in the
   substitution of full-caps, the behavior is the same as for
   text-transform.

  C.4.69 Section 15.6 Font boldness

   The text for this section (formerly part of 15.2.3) has been reverted
   to its CSS1 format. Also, discussion of font-weight from other parts of
   the Fonts chapter has been aggregated under this section.

   Removed statement that says "User agents must map names to values in a
   way that preserves visual order; a face mapped to a value must not be
   lighter than faces mapped to lower values." This is otherwise implied
   by "The only guarantee is that a face of a given value will be no less
   dark than the faces of lighter values."

  C.4.70 Section 15.7 Font size

   Clarified relationship of font size to em squares.

   Added a totally irrelevant note about font sizes virtual reality
   scenes.

  C.4.71 Section 16.1 Indentation

   Clarified that text overflowing due to text-indent is affected by the
   'overflow' property.

   Added a note about text-indents inheriting behavior and suggesting
   'text-indent: 0' on inline-blocks.

  C.4.72 Section 16.2 Alignment

   Changed "double justify" to "justify" under "left, right, center, and
   justify".

  C.4.73 Section 16.3.1 Underlining, over lining, striking, and blinking

   Added an example to illustrate how underlining affects descendant
   boxes.

  C.4.74 Section 16.5 Capitalization

   Switched language reference from RFC2070 to BCP47.

  C.4.75 Section 16.6 White space

   Added section 16.6.1 as an example to illustrate the interaction of
   white space collapsing and bidi.

  C.4.76 Section 17.1 Introduction to tables

   Expanded introduction to include a brief discussion of the two table
   layout models. Mentioned that the automatic table algorithm is not
   fully defined in CSS 2.1 but that some implementations have achieved
   relatively close interoperability.

  C.4.77 Section 17.2 The CSS table model

   Clarify that all table captions must be rendered if more than one
   exists.

   Specified that replaced elements with table display values are treated
   as table elements in table layout.

  C.4.78 Section 17.2.1 Anonymous table objects

   Moved the first bullet text to the prose before the list of generation
   rules as it is a general statement of what the rules are supposed to
   accomplish.

  C.4.79 Section 17.4 Tables in the visual formatting model

   Clarified that "display: table" elements behave as block-level elements
   and "display: inline-table" elements behave as inline-level elements
   and not the other way around.

   Clarified that 'table-caption' boxes behave as normal block boxes
   within the outer anonymous table box.

   Clarified that percentage 'width' and 'height' on the table box is
   relative to the anonymous box's containing block, not the anonymous box
   itself.

   Clarified that the 'position', 'float', 'top', 'right', 'bottom', and
   'left' values on the table box are used on the anonymous outer box
   instead of the table box and that the table box itself uses the initial
   values of those properties.

  C.4.80 Section 17.5 Visual layout of table contents

   To remove ambiguity about the position of extent of internal table
   boxes, the following paragraph was added after point 6:

     the edges of the rows, columns, row groups and column groups in the
     collapsing borders model coincide with the hypothetical grid lines
     on which the borders of the cells are centered. (And thus, in this
     model, the rows together exactly cover the table, leaving no gaps;
     ditto for the columns.) In the separated borders model, the edges
     coincide with the border edges of cells. (And thus, in this model,
     there may be gaps between the rows and columns, corresponding to the
     'border-spacing' property.)

   Changed warning note about positioning of table cells to be more
   precise about the possibly unintended effects.

  C.4.81 Section 17.5.1 Table layers and transparency

   At the end of the section added the following paragraph:

     Note that if the table has 'border-collapse: separate', the
     background of the area given by the 'border-spacing' property is
     always the background of the table element. See 17.6.1

  C.4.82 Section 17.5.2 Table width algorithms

   Added a paragraph to clarify the interaction of the table width
   algorithms with the rules in section 10.3 (Calculating widths and
   margins).

  C.4.83 Section 17.5.2.1 Fixed table layout

   Explicitly mentioned that the fixed table layout algorithm may be used
   with the algorithm of section 10.3.3 when 'table-layout' is 'fixed' but
   'width' is 'auto'.

  C.4.84 Section 17.5.2.2 Automatic table layout

   Clarified that UAs can use other algorithms besides the one in this
   section even if it results in different behavior. Also marked the rest
   of the section non-normative in accordance with that statement.

  C.4.85 Section 17.5.4 Horizontal alignment in a column

   Changed "The horizontal alignment of a cell's content within a cell box
   is specified with the 'text-align' property" to "The horizontal
   alignment of a cell's [INS: inline content :INS] within a cell box
   [INS: can be :INS] specified with the 'text-align' property."

  C.4.86 Section 17.5.5 Dynamic row and column effects

   Clarified that not affecting layout means that 'visibility: collapse'
   causes the part of row- and column-spanning cells that span into the
   collapsed row to be clipped.

  C.4.87 Section 17.6.1 The separated borders model

   Added a note explaining that 'border-spacing' can be used as a
   substitute for the non-standard 'framespacing' attribute on frameset
   elements (which are out-of-scope for CSS2.1).

   Added clarification about backgrounds: the sentence "This space is
   filled with the background of the table element" was replaced by:

     In this space, the row, column, row group, and column group
     backgrounds are invisible, allowing the table background to show
     through.

  C.4.88 Section 17.6.2 The collapsing borders model

   In the sentence after the question, added "and padding-left[i] and
   padding-right[i] refer to the left (resp., right) padding of cell i."

  C.4.89 Section 18.2 System Colors

   Noted that system colors are deprecated in CSS3.

  C.4.90 Section 18.4 Dynamic outlines

   Clarified that outlines do not cause overflow.

   Clarified that outlines are only fully connected "if possible".

  C.4.91 Section 18.4.1 Outlines and the focus

   Clarify that changing outlines in response to focus should not cause a
   document to reflow.

  C.4.92 Appendix D Default style sheet for HTML 4

   Added paragraph clarifying that some presentational markup in HTML can
   be replaced with CSS, but it requires different markup.

C.5 Errata since the Candidate Recommendation of July 2007

   Errata to CSS 2.1 since CR version of July 19, 2007.

  C.5.1 Section 1.4.2.1 Value

   [2009-04-15] The notation “&&” may be used in syntax definitions in
   future CSS specifications.

  C.5.2 Section 2.3 The CSS 2.1 processing model

   [2008-08-19] The first part of the section is not normative.

  C.5.3 Section 3.1 Definitions

   [2007-11-14] Append "[INS: For raster images without reliable
   resolution information, a size of 1 px unit per image source pixel must
   be assumed. :INS] " to the definition of "intrinsic dimensions."

  C.5.4 Section 4.1.1 Tokenization

   [2007-09-27] Remove "DELIM?" from the grammar rule
declaration : [DEL: DELIM? :DEL]  property S* ':' S* value;

   The DELIM was allowed there so that unofficial properties could start
   with a dash (-), but the dash was already allowed because of the
   definition of "IDENT."

   [2009-02-02] Change [DEL: U :DEL] to [INS: u :INS] in token
   UNICODE-RANGE. (It means the same, but seems to avoid confusion.)

   [2009-02-02] Clarify where comments are allowed:

     COMMENT tokens do not occur in the grammar (to keep it readable),
     but any number of these tokens may appear anywhere [DEL: between
     :DEL] [INS: outside :INS] other tokens. [INS: (Note, however, that a
     comment before or within the @charset rule disables the @charset.)
     :INS]

  C.5.5 Section 4.1.2.2 Informative Historical Notes

   [2008-12-09] Other known vendor prefixes are: -xv-, -ah-, prince-,
   -webkit-, and -khtml-.

  C.5.6 Section 4.1.3 Characters and case

   [2007-11-14] In the second bullet, change "[DEL: [a-z0-9] :DEL] " to
   "[INS: [a-zA-Z0-9] :INS] "; in the third bullet, change "[DEL: [0-9a-f]
   :DEL] " to "[INS: [0-9a-fA-F] :INS] ".

   Although the preceding bullet already says that CSS is
   case-insensitive, the explicit mention of upper and lower case letters
   helps avoid mistakes.

  C.5.7 Section 4.1.3 Characters and case

   [2008-03-05] CSS is now case-sensitive, except for certain parts:

     All CSS syntax is case-insensitive [INS: within the ASCII range
     (i.e., [a-z] and [A-Z] are equivalent) :INS] , except for parts that
     are not under the control of CSS.

  C.5.8 Section 4.1.3 Characters and case

   [2008-12-02] The pair “*/” ends a comment, even if preceded by a
   backslash. Change this sentence in the third bullet:

     [INS: Except within CSS comments, :INS] any character (except a
     hexadecimal digit) can be escaped with a backslash to remove its
     special meaning.

  C.5.9 Section 4.1.3 Characters and case

   [2009-04-15] Text added to match the grammar:

     […] any character (except a hexadecimal digit [INS: , linefeed,
     carriage return or form feed :INS] ) can be escaped […]

  C.5.10 Section 4.1.5 At-rules

   [2009-04-15] Clarified that unknown statements are ignored when looking
   for @import:

     CSS 2.1 user agents must ignore any '@import' rule that occurs
     inside a block or after any [DEL: valid :DEL] [INS: non-ignored
     :INS] statement other than an @charset or an @import rule.

  C.5.11 Section 4.1.7 Rule sets, declaration blocks, and selectors

   [2008-11-26] More precise statement of what is ignored:

     When a user agent cannot parse the selector (i.e., it is not valid
     CSS 2.1), it must ignore the [INS: selector and the following :INS]
     declaration block [INS: (if any) :INS] as well.

  C.5.12 Section 4.2 Rules for handling parsing errors

   [2009-04-15] Added error recovery rule for unexpected tokens at the top
   level:

     Malformed statements. User agents must handle unexpected tokens
     encountered while parsing a statement by reading until the end of
     the statement, while observing the rules for matching pairs of (),
     [], {}, "", and '', and correctly handling escapes. For example, a
     malformed statement may contain an unexpected closing brace or
     at-keyword. E.g., the following lines are all ignored:
p @here {color: red}     /* ruleset with unexpected at-keyword "@here" */
@foo @bar;               /* at-rule with unexpected at-keyword "@bar" */
}} {{ - }}               /* ruleset with unexpected right brace */
) [ {} ] p {color: red } /* ruleset with unexpected right parenthesis */

  C.5.13 Section 4.2 Rules for handling parsing errors

   [2008-11-26] Change “or block” as follows:

     User agents must ignore an invalid at-keyword together with
     everything following it, up to and including the next semicolon (;),
     [DEL: or block ({...}) :DEL] [INS: the next block ({...}), or the
     end of the block (}) that contains the invalid at-keyword :INS] ,
     whichever comes first.

  C.5.14 Section 4.3.2 Lengths

   [2008-08-19] Add recommendation about size of px:

     […] the user agent should rescale pixel values. [INS: It is
     recommended that the pixel unit refer to the whole number of device
     pixels that best approximates the reference pixel. :INS]

  C.5.15 Section 4.3.5 Counters

   [2008-03-05] Insert "case-sensitive" in "Counters are denoted by [INS:
   case-sensitive :INS] identifiers".

  C.5.16 Section 5.8.1 Matching attributes and attribute values

   [2008-04-07] Clarified ~= and |= by using the definitions from the
   Selectors module.

   [2008-11-03] Clarified that [foo~=""] (i.e., with an empty value) will
   not match anything.

  C.5.17 Section 5.8.2 Default attribute values in DTDs

   [2007-11-14] Replace "[DEL: tag :DEL] selector" by "[INS: type :INS]
   selector".

  C.5.18 Section 5.11.4 The language pseudo-class: :lang

   [2009-04-15] The language code is case-insensitive.

  C.5.19 Section 5.12.3 The :before and :after pseudo-elements

   [2008-11-03] Clarified text:

     When the :first-letter and :first-line pseudo-elements are [DEL:
     combined with :DEL] [INS: applied to an element having content
     generated using :INS] :before and :after, they apply to the first
     letter or line of the element including the [DEL: inserted text
     :DEL] [INS: generated content :INS] .

  C.5.20 Section 6.3 The @import rule

   [2008-08-19] Add “In CSS 2.1” and “See the section on parsing for when
   user agents must ignore @import rules” to

     [INS: In CSS 2.1, :INS] any @import rules must precede all other
     rules (except the @charset rule, if present). [INS: See the section
     on parsing for when user agents must ignore @import rules. :INS]

  C.5.21 Section 6.3 The @import rule

   [2008-11-26] Define what it means to import a style sheet twice and how
   the media list is matched. Add at the end:

     In the absence of any media types, the import is unconditional.
     Specifying 'all' for the medium has the same effect. [INS: The
     import only takes effect if the target medium matches the media
     list. :INS]

     [INS: A target medium matches a media list if one of the items in
     the media list is the target medium or 'all'. :INS]

     [INS: Note that Media Queries [MEDIAQ] extends the syntax of media
     lists and the definition of matching. :INS]

     [INS: When the same style sheet is imported or linked to a document
     in multiple places, user agents must process (or act as though they
     do) each link as though the link were to a separate style sheet.
     :INS]

  C.5.22 Section 6.4.1 Cascading order

   [2007-11-22] Spelling error: "prece[DEL: n :DEL] dence".

  C.5.23 Section 6.4.1 Cascading order

   [2008-11-26] Define the meaning of a media list:

     Find all declarations that apply to the element and property in
     question, for the target media type. Declarations apply if the
     associated selector matches the element in question [INS: and the
     target medium matches the media list on all @media rules containing
     the declaration and on all links on the path through which the style
     sheet was reached. :INS]

  C.5.24 Section 7.2.1 The @media rule

   [2008-12-02] The rules for parsing unknown statements inside @media
   blocks were ambiguous. Change the first sentence as follows:

     An @media rule specifies the target media types (separated by
     commas) of a set of [DEL: rules :DEL] [INS: statements :INS]
     (delimited by curly braces). [INS: Invalid statements must be
     ignored per 4.1.7 "Rule sets, declaration blocks, and selectors" and
     4.2 "Rules for handling parsing errors." :INS]

   Also make it explicit that CSS level 2 (unlike higher levels) has no
   nested @-rules. Add at the end of the section: “[INS: At-rules inside
   @media are invalid in CSS 2.1. :INS] ”

  C.5.25 Section 8.3.1 Collapsing margins

   [2008-08-18] In bullet 6, sub-bullet 2, the position of the top border
   edge is determined by assuming the element has a non-zero bottom (not:
   top) border.

  C.5.26 Section 8.3.1 Collapsing margins

   [2009-02-02] Rephrased the rule for adjoining margins so that the
   'min-height' and 'max-height' of an element have no influence over
   whether the element's bottom margin is adjoining to its last child's
   bottom margin.

  C.5.27 Section 8.3.1 Collapsing margins

   [2008-12-02] Not only elements with 'overflow' other than 'visible',
   but all block formatting contexts avoid collapsing their margins with
   their children. Change the third bullet as follows:

     * Vertical margins of elements [DEL: with 'overflow' other than
       'visible' :DEL] [INS: that establish new block formatting contexts
       (such as floats and elements with 'overflow' other than 'visible')
       :INS] do not collapse with their in-flow children.

  C.5.28 Section 9.2.2 Inline-level elements and inline boxes

   [2008-12-02] Added missing 'inline-block' in: “Several values of the
   'display' property make an element inline: 'inline', 'inline-table',
   [INS: 'inline-block' :INS] and 'run-in' (part of the time; see run-in
   boxes).”

  C.5.29 Section 9.2.4 The 'display' property

   [2008-04-07] Clarified that 'display: none' also applies to non-visual
   media.

  C.5.30 Section 9.3.2 Box offsets: 'top', 'right', 'bottom', 'left'

   [2008-08-19] Remove true but confusing note (occurs 4×):

     [DEL: Note: For absolutely positioned elements whose containing
     block is based on a block-level element, this property is an offset
     from the padding edge of that element. :DEL]

  C.5.31 Section 9.5 Floats

   [2008-08-19] Positioned descendants of a float are in the stacking
   context of the float's parent. Add “positioned elements and” to

     […] except that any [INS: positioned elements and :INS] elements
     that actually create new stacking contexts take part in the float's
     parent's stacking context.

   Same change in Section 9.9 Layered presentation:

     […] except that any [INS: positioned elements and :INS] any elements
     that actually create new stacking contexts take part in the parent
     stacking context.”

  C.5.32 Section 9.5 Floats

   [2008-12-02] Remove “'s” that may be misinterpreted: “the float's
   parent[DEL: 's :DEL] stacking context.”

  C.5.33 Section 9.5.2 Controlling flow next to floats: the 'clear' property

   [2009-02-02] Add an example of negative clearance after the first note.

  C.5.34 Section 9.6.1 Fixed positioning

   [2008-11-03] Added:

     [INS: Boxes with fixed position that are larger than the page box
     are clipped. Parts of the fixed position box that are not visible in
     the initial containing block will not print. :INS]

  C.5.35 Section 9.9.1 Specifying the stack level: the 'z-index' property

   [2008-12-02] The list of stacking levels is ambiguous: relatively
   positioned elements could fall under items 3/4/5 or under item 6. Meant
   is item 6, so exclude them from 3/4/5 as follows:

    1. the background and borders of the element forming the stacking
       context.
    2. the stacking contexts of descendants with negative stack levels.
    3. a stacking level containing in-flow non-inline-level [INS:
       non-positioned :INS] descendants.
    4. a stacking level for [INS: non-positioned :INS] floats and their
       contents.
    5. a stacking level for in-flow inline-level [INS: non-positioned
       :INS] descendants.
    6. a stacking level for positioned descendants with 'z-index: auto',
       and any descendant stacking contexts with 'z-index: 0'.
    7. the stacking contexts of descendants with positive stack levels.

  C.5.36 Section 10.1 Definition of "containing block"

   [2009-02-02] Rephrase first bullet point to make easier to read:

     [DEL: The containing block in which the root element lives is a
     rectangle with the dimensions of the viewport, anchored at the
     canvas origin for continuous media, and the page area for paged
     media. This containing block is called the initial containing block.
     :DEL]

     [INS: The containing block in which the root element lives is a
     rectangle called the initial containing block. For continuous media,
     it has the dimensions of the viewport and is anchored at the canvas
     origin; it is the page area for paged media. :INS]

  C.5.37 Section 10.3 Calculating widths and margins

   [2009-04-15] The values of 'left' and 'right' are only determined by
   section 9.4.3 in the case of relatively positioned elements:

     For Points 1-6 and 9-10, the values of 'left' and 'right' [DEL: used
     for layout :DEL] [INS: in the case of relatively positioned elements
     :INS] are determined by the rules in section 9.4.3.

  C.5.38 Section 10.3.1 Inline, non-replaced elements

   [2009-04-15] The only case in which 'left' or 'right' can be 'auto' is
   when the element is statically positioned. In that case 'left' and
   'right are ignored and there is thus no need to determine a used value:

     A computed value of 'auto' for [DEL: 'left', 'right', :DEL]
     'margin-left' or 'margin-right' becomes a used value of '0'.

  C.5.39 Section 10.3.2 Inline, replaced elements

   [2007-11-14] Add the following paragraph:

     [INS: Otherwise, if 'width' has a computed value of 'auto', and the
     element has an intrinsic width, then that intrinsic width is the
     used value of 'width'. :INS]

   just before the paragraph beginning "Otherwise, if 'width' has a
   computed value of 'auto', but none of the conditions above are met,
   […]".

  C.5.40 Section 10.3.2 Inline, replaced elements

   [2008-03-05] Change the last paragraph as follows:

     If it does, [DEL: then a percentage intrinsic width on that element
     cannot be resolved and the element is assumed to have no intrinsic
     width :DEL] [INS: then the resulting layout is undefined in CSS2.1
     :INS] .

  C.5.41 Section 10.3.3 Block-level, non-replaced elements in normal flow

   [2008-03-05] Scrollbar widths are no longer included in the containing
   block width. Remove scrollbar width from:

     'margin-left' + 'border-left-width' + 'padding-left' + 'width' +
     'padding-right' + 'border-right-width' + 'margin-right' [DEL: +
     scrollbar width (if any) :DEL] = width of containing block

   and from:

     If 'width' is not 'auto' and 'border-left-width' + 'padding-left' +
     'width' + 'padding-right' + 'border-right-width' [DEL: + scrollbar
     width (if any) :DEL] [...]

   and remove the paragraph:

     [DEL: The "scrollbar width" value is only relevant if the user agent
     uses a scrollbar as its scrolling mechanism. See the definition of
     the 'overflow' property. :DEL]

  C.5.42 Section 10.3.7 Absolutely positioned, non-replaced elements

   [2008-03-05] Scrollbar widths are no longer included in the containing
   block width. Remove scrollbar width from:

     'left' + 'margin-left' + 'border-left-width' + 'padding-left' +
     'width' + 'padding-right' + 'border-right-width' + 'margin-right' +
     'right' [DEL: + scrollbar width (if any) :DEL] = width of containing
     block

   and remove the paragraph:

     [DEL: The "scrollbar width" value is only relevant if the user agent
     uses a scrollbar as its scrolling mechanism. See the definition of
     the 'overflow' property. :DEL]

  C.5.43 Section 10.3.7 Absolutely positioned, non-replaced elements

   [2008-03-05] Add the following definition.

   [2008-08-19] Add the following note to that definition.

     [INS: The static-position containing block is the containing block
     of a hypothetical box that would have been the first box of the
     element if its specified 'position' property had been 'static' and
     its 'float' had been 'none'. (Note that due to the rules in section
     9.7 this hypothetical calculation might require also assuming a
     different computed value for 'display'.) :INS]

   And change which 'direction' property is used as follows (two
   occurrences):

     [...] if the 'direction' property of the [INS: element establishing
     the static-position :INS] containing block is [...]

  C.5.44 Section 10.3.8 Absolutely positioned, replaced elements

   [2008-03-05] Change bullet 2 as follows:

     [...] if [INS: the :INS] 'direction' [INS: property :INS] of the
     [INS: element establishing the static-position :INS] containing
     block is [...]

  C.5.45 Section 10.3.8 Absolutely positioned, replaced elements

   [2008-03-05] Clarification. Replace

     [DEL: This situation is similar to the previous one, except that the
     element has an intrinsic width. The sequence of substitutions is
     now: :DEL]

   by

     [INS: In this case, section 10.3.7 applies up through and including
     the constraint equation, but the rest of section 10.3.7 is replaced
     by the following rules: :INS]

  C.5.46 Section 10.3.8 Absolutely positioned, replaced elements

   [2008-04-07] Clarified that margins are not calculated as for inline
   elements.

  C.5.47 Section 10.5 Content height: the 'height' property

   Under “<percentage>,” add the same note as under “<percentage>,” in
   section 10.2 (“Content width: the 'width' property”).

  C.5.48 Section 10.6.2 Inline replaced elements […]

   [2007-11-14] Add the following paragraph:

     [INS: Otherwise, if 'height' has a computed value of 'auto', and the
     element has an intrinsic height, then that intrinsic height is the
     used value of 'height'. :INS]

   just before the paragraph beginning "Otherwise, if 'height' has a
   computed value of 'auto', but none of the conditions above are met
   […]".

  C.5.49 Section 10.6.4 Absolutely positioned, non-replaced elements

   [2008-11-26] The static position is determined considering neither
   float nor clear. Add this:

     […] and its specified 'float' had been 'none' [INS: and 'clear' had
     been 'none' :INS] .

  C.5.50 Section 10.6.5 Absolutely positioned, replaced elements

   [2008-04-07] Clarified that margins are not calculated as for inline
   elements.

  C.5.51 Section 10.8.1 Leading and half-leading

   [2007-11-14] In the Note under 'vertical-align', remove "slightly" from
   "Values of this property have [DEL: slightly :DEL] different meanings
   in the context of tables."

  C.5.52 Section 11.1.1 Overflow: the 'overflow' property

   [2008-03-05] Scrollbar widths are no longer included in the containing
   block width. Replace

     [DEL: The space taken up by the scrollbars affects the computation
     of the dimensions in the rendering model. :DEL]

   by

     [INS: Any space taken up by the scrollbars should be taken out of
     (subtracted from the dimensions of) the containing block formed by
     the element with the scrollbars. :INS]

   [2008-11-03] 'Overflow' on BODY is special not only in HTML but also in
   XHTML. Change the sentence “[DEL: HTML UAs must instead apply the
   'overflow' property from the BODY element to the viewport, if the value
   on the HTML element is 'visible'. :DEL] ” to:

     [INS: When the root element is an HTML "HTML" element or an XHTML
     "html" element, and that element has an HTML "BODY" element or an
     XHTML "body" element as a child, user agents must instead apply the
     'overflow' property from the first such child element to the
     viewport, if the value on the root element is 'visible'. :INS]

  C.5.53 Section 11.1.2 Clipping: the 'clip' property

   [2008-03-05] Insert "(but not a combination)" in "User agents must
   support separation with commas, but may also support separation without
   commas [INS: (but not a combination) :INS] ".

  C.5.54 Section 12.2 The 'content' property

   [2009-04-15] (And also in section 12.4:) certain keywords, in
   particular 'none', 'inherit' and 'initial' (the latter being reserved
   for future use) cannot be used as names for counters.

  C.5.55 Section 12.4.2 Counter styles

   [2008-03-05] Error in example. Replace hebrew by lower-greek:
BLOCKQUOTE:after { content: " [" counter(bq, [DEL: hebrew :DEL]  [INS: lower-gre
ek :INS] ) "]" }

  C.5.56 Section 12.5 Lists

   [2008-12-01] Change “in” to “with respect to” in

     The list properties describe basic visual formatting of lists: they
     allow style sheets to specify the marker type (image, glyph, or
     number), and the marker position [DEL: in :DEL] [INS: with respect
     to :INS] the principal box (outside it or within it before content).

   because the marker is, as the rest of the sentence itself makes clear,
   not necessarily in the principal box.

  C.5.57 Section 12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   [2008-04-07] The size of list style markers without an intrinsic size
   is now defined.

  C.5.58 Section 12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   [2008-12-01] CSS 2.1 does not specify the position of the list item
   marker, but does require it to be on the left or right of the content.
   Also, the marker is not affected by 'overflow', but may influence the
   height of the principal box. Add to the definition of 'outside':

     [INS: … but does require that for list items whose 'direction'
     property is 'ltr' the marker box be on the left side of the content
     and for elements whose 'direction' property is 'rtl' the marker box
     be on the right side of the content. 'Overflow' on the element does
     not clip the marker box. The marker box is fixed with respect to the
     principal block box's border and does not scroll with the principal
     block box's content. The size or contents of the marker box may
     affect the height of the principal block box and/or the height of
     its first line box, and in some cases may cause the creation of a
     new line box. Note: This interaction may be more precisely defined
     in a future level of CSS. :INS]

  C.5.59 Section 12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   [2009-04-015] Meaning of 'none' for 'list-style' was only defined by an
   example.

  C.5.60 Section 13.2 Page boxes: the @page rule

   [2008-08-19] Add rules for drawing canvas to:

     * The page area. The page area includes the boxes laid out on that
       page. The edges of the first page area establish the rectangle that
       is the initial containing block of the document. [INS: The canvas
       background is painted within and covers the page area. :INS]
     * The margin area, which surrounds the page area. [INS: The page
       margin area is transparent. :INS]

  C.5.61 Section 13.2.1.1 Rendering page boxes that do not fit a target sheet

   [2009-02-02]

   Remove sections 13.2.1.1 and 13.2.1.2. (The described situations cannot
   occur in CSS 2.1, because CSS 2.1 does not have a 'size' property.)

  C.5.62 Section 13.2.3 Content outside the page box

   [2008-11-03] Clarified what locations are inconvenient for printing:

     When formatting content in the page model, some content may end up
     outside the [INS: current :INS] page box. For example, an element
     whose 'white-space' property has the value 'pre' may generate a box
     that is wider than the page box. [INS: As another example, :INS]
     when boxes are positioned absolutely [INS: or relatively :INS] ,
     they may end up in “inconvenient” locations. For example, images may
     be placed on the edge of the page box or 100,000 meters below the
     page box.

  C.5.63 Section 13.3.1 Page break properties: 'page-break-before',
  'page-break-after', 'page-break-inside'

   [2008-04-30] The 'page-break-inside' property no longer inherits.

  C.5.64 Section 13.3.1 Page break properties: 'page-break-before',
  'page-break-after', 'page-break-inside'

   [2008-12-01] UAs may apply 'page-break-before', 'page-break-after' and
   'page-break-inside' to other elements than block-level ones.

  C.5.65 Section 13.3.2 Breaks inside elements: 'orphans', 'widows'

   [2009-02-02] “Paragraph” is not a defined term. Change [DEL: of a
   paragraph :DEL] to [INS: in a block element :INS] (twice).

  C.5.66 Section 13.3.2 Breaks inside elements: 'orphans', 'widows'

   [2009-04-15] 'Widows' and 'orphans' only accept positive values.

  C.5.67 Section 13.3.3 Allowed page breaks

   [2008-04-30] The 'page-break-inside' property of all ancestors is
   checked for page-breaking restrictions, not just that of the
   breakpoint's parent.

  C.5.68 Section 13.3.3 Allowed page breaks

   [2009-02-02] Remove possible confusion:

     Rule D: In addition, breaking at (2) is allowed only if the
     'page-break-inside' property of [INS: the element and :INS] all
     [INS: its :INS] ancestors is 'auto'.

  C.5.69 Section 13.3.3 Allowed page breaks

   [2009-02-02] Top margins do not disappear at a page break that is
   forced by a 'page-break-after' or 'page-break-before'. Correct the
   first bullet to:

     When an [INS: unforced :INS] page break occurs here, the used values
     of the relevant 'margin-top' and 'margin-bottom' properties are set
     to '0'. [INS: When a forced page break occurs here, the used value
     of the relevant 'margin-bottom' property is set to '0'; the relevant
     'margin-top' used value may either be set to '0' or retained. :INS]

   And add the following note:

     [INS: Note: It is expected that CSS3 will specify that the relevant
     'margin-top' applies (i.e., is not set to '0') after a forced page
     break. :INS]

  C.5.70 Section 13.3.5 "Best" page breaks

   [2009-02-02] Remove the advice to user agents to avoid breaking inside
   elements with borders, inside tables or inside floating elements; add
   the advice to avoid breaking inside replaced elements.

  C.5.71 Section 14.2 The background

   [2008-11-03] The 'background' property is special on BODY not only in
   HTML but also in XHTML.

  C.5.72 Section 14.2 The background

   [2009-04-15] The whole 'background' property is used for the canvas,
   not just the color and the image:

     For documents whose root element is an HTML "HTML" element or an
     XHTML "html" element that has computed values of 'transparent' for
     'background-color' and 'none' for 'background-image', user agents
     must instead use the computed value of [DEL: those :DEL] [INS: the
     background :INS] properties from that element's first HTML "BODY"
     element or XHTML "body" element child […]

  C.5.73 Section 14.2.1 Background properties: 'background-color',
  'background-image', 'background-repeat', 'background-attachment',
  'background-position', and 'background'

   [2008-04-07] The size of background images without an intrinsic size is
   now defined.

  C.5.74 Section 15.6 Font boldness: the 'font-weight' property

   [2008-11-26] Remove incorrect text:

     * 'bolder' selects the next weight that is assigned to a font that is
       darker than the inherited one. [DEL: If there is no such weight, it
       simply results in the next darker numerical value (and the font
       remains unchanged), unless the inherited value was '900' in which
       case the resulting weight is also '900'. :DEL]
     * 'lighter' is similar, but works in the opposite direction: it
       selects the next lighter keyword with a different font from the
       inherited one, [DEL: unless there is no such font, in which case it
       selects the next lighter numerical value (and keeps the font
       unchanged) :DEL] .

   and:

     [DEL: The computed value of "font-weight" is either: :DEL]
     * [DEL: one of the legal number values, or :DEL]
     * [DEL: one of the legal number values combined with one or more of
       the relative values (bolder or lighter). This type of computed
       values is necessary to use when the font in question does not have
       all weight variations that are needed. :DEL]

   And instead add this note:

     [INS: Note: A set of nested elements that mix 'bolder' and 'lighter'
     will give unpredictable results depending on the UA, OS, and font
     availability. This behavior will be more precisely defined in CSS3.
     :INS]

  C.5.75 Section 16.6 Whitespace: the 'white-space' property

   [2008-08-19] Remove rules about generated text from:

     The following examples show what whitespace behavior is expected
     from the PRE and P elements, the “nowrap” attribute in HTML, [DEL:
     and in generated content :DEL] .
pre        { white-space: pre }
p          { white-space: normal }
td[nowrap] { white-space: nowrap }
[DEL: :before,:after { white-space: pre-line } :DEL]

  C.5.76 Section 16.6.1 The 'white-space' processing model

   [2009-02-02] Collapsing of white space does not remove any line
   breaking opportunities. Add the following clarification:

     Then, the entire block is rendered. Inlines are laid out, taking
     bidi reordering into account, and wrapping as specified by the
     'white-space' property. [INS: When wrapping, line breaking
     opportunities are determined based on the text prior to the white
     space collapsing steps above. :INS]

  C.5.77 Section 17.2.1 Anonymous table objects

   [2007-11-14] Spelling error: "boxes[DEL: s :DEL] ".

  C.5.78 Section 17.2.1 Anonymous table objects

   [2008-10-13] Added new rule after bullet 4:

     [INS: 5. If a child T of a 'table', 'inline-table',
     'table-row-group', 'table-header-group', 'table-footer-group', or
     'table-row' box is an anonymous inline box that contains only white
     space, then it is treated as if it has 'display: none'. :INS]

  C.5.79 Section 17.4 Tables in the visual formatting model

   [2009-02-02] The anonymous block containing the table and its caption
   establishes a block formatting context:

     The anonymous box is a 'block' box if the table is block-level, and
     an 'inline-block' box if the table is inline-level [DEL: except that
     this block is never considered as a block for 'run-in' interaction,
     and that :DEL] [INS: The anonymous box establishes a block
     formatting context. :INS] The table box (not the anonymous box) is
     used when doing baseline vertical alignment for an 'inline-table'.

   The diagram now shows the caption's margins inside the anonymous box.

  C.5.80 Section 17.5.4 Horizontal alignment in a column

   [2008-04-07] Clarification:

     The horizontal alignment of a cell's [INS: inline :INS] content
     within a cell box [DEL: is :DEL] [INS: can be :INS] specified [DEL:
     with the 'text-align' property :DEL] [INS: by the value of the
     'text-align' property on the cell :INS] .

  C.5.81 Section 18.1 Cursors: the 'cursor' property

   [2008-04-07] The size of cursors without an intrinsic size is now
   defined.

  C.5.82 Section B.2 Informative references

   [2007-11-14] Spelling error: change "[DEL: ? :DEL] lik" to "[INS: Ç
   :INS] elik" (2×).

  C.5.83 Appendix D. Default style sheet for HTML 4

   [2008-08-19] Replace
br:before       { content: "\A" }
:before, :after { white-space: pre-line }

   with
br:before       { content: "\A"; white-space: pre-line }

  C.5.84 Appendix D. Default style sheet for HTML 4

   [2008-08-19] Add tr to:
td, th[INS: , tr :INS]       { vertical-align: inherit }

  C.5.85 Section E.2 Painting order

   [2007-11-14] Replace "but any descendants which actually create a new
   stacking context" by "but any [INS: positioned descendants and :INS]
   descendants which actually create a new stacking context".

  C.5.86 Appendix G. Grammar of CSS 2.1

   [2007-09-27] Change the last "S" in the grammar rule for "combinator"
   to "S+":
combinator
  : PLUS S*
  | GREATER S*
  | S[INS: + :INS]

   and remove the rule
[DEL: {s}+\/\*[^*]*\*+([^/*][^*]*\*+)*\/  {unput(' '); /*replace by space*/} :DE
L]

   in the tokenizer. The resulting language is the same, but the grammar
   is easier to read and relies less on specific notations of Flex.

  C.5.87 Section G.1 Grammar

   [2007-09-27] Changes to remove ambiguity with respect to the S token
   and avoid nullable non-terminals.

  C.5.88 Section G.2 Lexical scanner

   [2007-09-27] Change the tokenizer rule
[DEL: @{C}{H}{A}{R}{S}{E}{T} :DEL]      {return CHARSET_SYM;}

   to
[INS: "@charset " :INS]   {return CHARSET_SYM;}

   The @charset must be in lowercase and must have a space after it (as
   defined in section  4.4 CSS style sheet representation).

  C.5.89 Section G.2 Lexical scanner

   [2008-03-05] Change the tokenizer rules
[DEL: "url :DEL] ("{w}{string}{w}")" {return URI;}
[DEL: "url :DEL] ("{w}{url}{w}")"    {return URI;}

   to
[INS: {U}{R}{L}" :INS] ("{w}{string}{w}")"      {return URI;}
[INS: {U}{R}{L}" :INS] ("{w}{url}{w}")" {return URI;}

  C.5.90 Section G.2 Lexical scanner

   [2008-04-07] The definition of the macro “O” is wrong. The letters O
   and o can be written with hexadecimal escapes as “\4f” and “\6f”
   respectively (not as “\51” and “\71”). The macro should therefore be
O               o|\\0{0,4}(4f|6f)(\r\n|[ \t\r\n\f])?|\\o

  C.5.91 Section G.2 Lexical scanner

   “The two occurrences of "\377"…”: There is in fact only one occurrence.

  C.5.92 Appendix I. Index

   Add a TITLE attribute to all links and which is equal to the lemma.

C.6 Errata since the Candidate Recommendation of April 2009

   These are the errata for CSS level 2 revision 1, CR version of 23 April
   2009. These corrections have the status of a draft.

  C.6.1 Section 4.2 Rules for handling parsing errors

   [2009-08-06] Clarified the rules for ignoring invalid at-keywords:

     Invalid at-keywords. User agents must ignore an invalid at-keyword
     together with everything following it, [INS: up to the end of the
     block that contains the invalid at-keyword, or :INS] up to and
     including the next semicolon (;), [INS: or up to and including :INS]
     the next block ({...}), [DEL: or the end of the block (}) that
     contains the invalid at-keyword, :DEL] whichever comes first.

  C.6.2 Section 13.3.3 Allowed page breaks

   [2009-08-06] Page breaks are also allowed when there is a gap after the
   last content of a block. Added the following to the first list:

     3. Between the content edge of a block box and the outer edges of
     its child content (margin edges of block-level children or line box
     edges for inline-level children) if there is a (non-zero) gap
     between them.

  C.6.3 Section 15.3 Font family: the 'font-family' property

   [2009-08-31] The list of keywords in “(e.g., 'initial', 'inherit',
   'default', 'serif', 'sans-serif', 'monospace', 'fantasy', and
   'cursive')” isn't an example, but is in fact the complete and normative
   list.

  C.6.4 Section 15.3.1.1 serif

   [2009-08-31] Spelling errors in font names. The correct names are
   “Excelsior Cyrillic Upright” and “ER Bukinist.”

  C.6.5 Section 15.7 Font size: the 'font-size' property

   [2009-08-31] The two notes “Note: implementation experience has
   demonstrated…” and “Note 2. In CSS1, the suggested scaling factor… say
   essentially the same thing. They are replaced by a single note:

     Note 2. In CSS1, the suggested scaling factor between adjacent
     indexes was 1.5, which user experience proved to be too large. In
     CSS2, the suggested scaling factor for a computer screen between
     adjacent indexes was 1.2, which still created issues for the small
     sizes. Implementation experience has demonstrated that a fixed ratio
     between adjacent absolute-size keywords is problematic, and this
     specification does not recommend such a fixed ratio.

  C.6.6 Section 17.5.2.1 Fixed table layout

   [2009-05-20] UAs may render extra columns if there are unexpected
   columns in later rows of a 'fixed' table layout. In that case, the
   width of the columns and of the table is undefined.

  C.6.7 Section 17.5.3 Table height layout

   [2009-08-06] Replaced “[DEL: Percentage heights on table cells, table
   rows, and table row groups compute to 'auto' :DEL] by

     [INS: CSS 2.1 does not define how the height of table cells and
     table rows is calculated when their height is specified using
     percentage values. CSS 2.1 does not define the meaning of 'height'
     on row groups. :INS]

  C.6.8 Appendix G. Grammar of CSS 2.1

   [2009-08-06] Removed ambiguities from the grammar. (The ambiguities
   only affected spaces and were harmless.)

C.7 Errata since the Candidate Recommendation of September 2009

   These are the errata for CSS level 2 revision 1, CR version of
   8 September 2009. These corrections have the status of a draft.

  C.7.1 Section 1.4.2.1 Value

   [2010-08-06] (Also in various other sections throughout the
   specification.) Distinguished all cases where the word value referred
   to a whole property value from where it referred to only part of such a
   value (such as a component in a comma-separated list). The former is
   now property value, the latter component value.

  C.7.2 Section 3.1 Definitions

   [2010-04-19] Add a clarification to the definition of replaced element:

     [INS: The content of replaced elements is not considered in the CSS
     rendering model. :INS]

   (Previously, the definition only said that the content was “outside the
   scope of CSS.”)

  C.7.3 Section 4.1.1 Tokenization

   [2010-04-19] The definition of “identifier” in 4.1.3 (2nd bullet) and
   in the grammar were contradictory w.r.t. whether no-break space
   (U+00A0) was allowed in identifiers or not. Change the text in 4.1.3 to
   allow no-break space: “characters [DEL: U+00A1 :DEL] [INS: U+00A0 :INS]
   and higher.”

   Also, change the macro “nonascii” in the token definition from “[DEL:
   [^\0-\177] :DEL] ” to [INS: [^\0-\237] :INS] ”. (When CSS was first
   written, Unicode didn't have code points U+0080 to U+009F, i.e.,
   \200-\237 in octal.)

  C.7.4 Section 4.1.1 Tokenization

   [2010-09-29] The tokenizer has been modified so that it can be
   implemented as a state machine without back-up (e.g., with Lex). This
   changes the meaning of an input of the form “url(…(…)…)”, i.e., input
   that starts like a URI token but then contains a parenthesis (which is
   not allowed in a URI token). Previously, such input was re-parsed to
   yield a FUNCTION token followed by other things; now it yields a
   BAD_URI token. Given that CSS has never used a FUNCTION token of the
   form “url(” this should not affect any existing CSS style sheets.

   A non-normative section has been added to appendix G with an
   explanation of how to make a tokenizer without back-up.

  C.7.5 Section 4.1.1 Tokenization

   [2010-09-29] The definition of the URI token was ambiguous: it allowed
   a backslash to be either parsed on its own or as part of an escape. A
   backslash in a URI token must always be interpreted as part of an
   escape.

  C.7.6 Section 4.1.1 Tokenization

   [2010-09-29] Error handling for illegal tokens (braces, at-keywords,
   and SGML comment tokens) inside parenthesized expressions was not well
   defined. Change the production for “any” as follows

any         : [ IDENT | NUMBER | PERCENTAGE | DIMENSION | STRING
              | DELIM | URI | HASH | UNICODE-RANGE | INCLUDES
              | DASHMATCH | ':' | FUNCTION S* [INS: [ :INS] any[INS: |unsused] :
INS] * ')'
              | '(' S* [INS: [ :INS] any[INS: |unused] :INS] * ')' | '[' S* [INS
: [ :INS] any[INS: |unused] :INS] * ']'
              ] S*;
[INS: unused      : block | ATKEYWORD S* | ';' S* | CDO S* | CDC S*; :INS]

   and add the following explanation:

     [INS: The "unused" production is not used in CSS and will not be
     used by any future extension. It is included here only to help with
     error handling. (See 4.2 "Rules for handling parsing errors.") :INS]

  C.7.7 Section 4.1.2.2 Informative Historical Notes

   [2010-04-19] Add “-tc-” to the list of existing vendor prefixes.

  C.7.8 Section 4.1.3 Characters and case

   [2010-08-06] The handling of a backslash before a newline or at the end
   of a file is no longer undefined: it is parsed as a DELIM.

  C.7.9 Section 4.1.3 Characters and case

   [2010-08-06] Make text and formal grammar the same:

     In CSS, identifiers […]; they cannot start with a digit, [INS: two
     hyphens, :INS] or a hyphen followed by a digit.

  C.7.10 Section 4.1.8 Declarations and properties

   [2010-05-12] Remove “2.1” from

     Every CSS [DEL: 2.1 :DEL] property has its own syntactic and
     semantic restrictions

  C.7.11 Section 4.2 Rules for handling parsing errors

   [2010-07-07] Clarify that the fifth bullet only applies to at-rules.
   (At-keywords in other constructs are already handled in the preceding
   bullets.)

     * [DEL: Invalid at-keywords :DEL] [INS: At-rules with unknown
       at-keywords :INS] . User agents must ignore…

  C.7.12 Section 4.3.2 Lengths

   [2010-04-19] Make explicit that 'ex', when used in the 'font-size'
   property, refers to the parent element's 'ex' (just as 'em' refers to
   the parent's 'em' in that case.)

  C.7.13 Section 4.3.2 Lengths

   [2010-10-28] A UA must now either display absolute lengths (cm, in, pt,
   etc.) at their real size or make px align with device pixel boundaries
   near the 0.0213 degrees viewing angle, but not both. In either case,
   3px must equal 4pt.

   (Until now, authors could use absolute lengths for physical sizes and
   px for aligning to device pixels, but couldn't know the number of pt in
   a px, except in combination with Media Queries. Authors can no longer
   choose between absolute or device-related units, but can use px and pt
   interchangeably. This should only affect relatively low-resolution
   devices: above 300 dots per inch, the maximum error is about 16%.)

  C.7.14 Section 4.3.4 URLs and URIs

   [2010-05-12] Commas do not have to be escaped in <uri> tokens:

     Some characters appearing in an unquoted URI, such as parentheses,
     [DEL: commas, :DEL] white space characters, single quotes (') and
     double quotes ("), must be escaped

  C.7.15 Section 4.3.4 URLs and URIs

   [2010-04-21] Describe in English what was only expressed through the
   grammar:

     [INS: Note. Since URIs may contain characters that would otherwise
     be used as delimiters in CSS, the entire URI value must be treated
     as a single unit by the tokenizer and normal tokenization behavior
     does not apply within a URI value. Therefore comments are not
     allowed within a URI value. :INS]

  C.7.16 Section 5.8.2 Default attribute values in DTDs

   [2010-09-29] Clarify what is meant by “is not required”:

     More precisely, a UA [INS: may, but :INS] is not required to[INS: ,
     :INS] read an "external subset" of the DTD but is required to look
     for default attribute values in the document's "internal subset."
     (See [XML10] for definitions of these subsets.) [INS: Depending on
     the UA, a default attribute value defined in the external subset of
     the DTD might or might not appear in the document tree. :INS]

     A UA that recognizes an XML namespace [XMLNAMESPACES] [INS: may, but
     :INS] is not required to[INS: , :INS] use its knowledge of that
     namespace to treat default attribute values as if they were present
     in the document. (E.g., an XHTML UA is not required to use its
     built-in knowledge of the XHTML DTD.)

   and:

     the first rule [DEL: will :DEL] [INS: might :INS] not match elements
     whose "notation" attribute is set by default, i.e., not set
     explicitly. To catch all cases, the attribute selector for the
     default value must be dropped:

  C.7.17 Section 5.11.4 The language pseudo-class: :lang

   [2010-08-06] The argument of ':lang()' is only case-insensitive for
   characters in ASCII.

  C.7.18 Section 5.12 Pseudo-elements

   [2010-08-06] Clarify that pseudo-elements behave like elements for the
   aspects not explicitly mentioned:

     [INS: Pseudo-elements behave just like real elements in CSS with the
     exceptions described below and elsewhere. :INS]

  C.7.19 Section 5.12.1 The :first-line pseudo-element

   [2010-08-24] More consistent use of “block” and “block-level.” Change:

     The :first-line pseudo-element can only be attached to a [DEL:
     block-level element, inline-block, table-caption or a table-cell
     :DEL] [INS: block container element :INS] .

  C.7.20 Section 5.12.2 The :first-letter pseudo-element

   [2010-08-24] More consistent use of “block” and “block-level.” Change:

     The :first-letter pseudo-element applies to [DEL: block, list-item,
     table-cell, table-caption and inline-block elements :DEL] [INS:
     block container elements :INS] .

  C.7.21 Section 6.2 Inheritance

   [2010-08-06] Add a note that, because it follows the document tree,
   inheritance is not intercepted by anonymous boxes

  C.7.22 Section 6.4.4 Precedence of non-CSS presentational hints

   [2010-10-05] Give other languages than HTML (such as SVG) the
   possibility to define certain attributes as “presentational
   attributes”:

     For other languages, all document language-based styling [DEL:
     should be handled in the user agent style sheet :DEL] [INS: must be
     translated to the corresponding CSS and either enter the cascade at
     the user agent level or, as with HTML presentational hints, be
     treated as author level rules with a specificity of zero placed at
     the start of the author style sheet :INS] .

  C.7.23 Section 7.3 Recognized media types

   [2010-09-08] Clarify what is ignored. Change:

     @media and @import rules with unknown media types [INS: (that are
     nonetheless valid identifiers) :INS] are treated as if the unknown
     media types are not present. [INS: If an @media/@import rule
     contains a malformed media type (not an identifier) then the
     statement is invalid. :INS]

     [INS: Note: Media Queries supercedes this error handling. :INS]

  C.7.24 Section 8.3.1 Collapsing margins

   [2010-05-12] Simplify/clarify text:

     An element that has [DEL: had :DEL] clearance [DEL: applied to it
     :DEL] never collapses

   and:

     When an element's own margins collapse, and that element has [DEL:
     had :DEL] clearance [DEL: applied to it :DEL]

  C.7.25 Section 8.3.1 Collapsing margins

   [2010-08-24] More consistent use of “block box” vs “block-level
   element.” Include table captions in the set of block-level elements.
   See also changes to 9.2.1 and to 9.2.1.1.

     Two or more adjoining vertical margins of block[INS: -level :INS]
     boxes in the normal flow collapse.

   and

     The top margin of an in-flow [DEL: block-level element :DEL] [INS:
     block box :INS] is adjoining to its first in-flow block-level
     child's top margin

   and

     The bottom margin of an in-flow [DEL: block-level element :DEL]
     [INS: block box :INS] with a 'height' of 'auto'

  C.7.26 Section 9.2.1 Block-level elements and block boxes

   [2010-08-24] Define the term “block-level element” more precisely. Also
   define auxiliary terms “block container box” and “block box”:

   More consistent use of block box vs block-level element in
   section 9.2.1.1. See also changes to section 8.3.1 and 9.4.

  C.7.27 Section 9.2.1.1 Anonymous block boxes

   [2010-05-12] The example has invalid HTML mark-up. Change it to use P
   and SPAN elements instead of BODY and P.

   [2010-08-06] Also clarify that “block box” only refers to boxes in the
   same flow.

  C.7.28 Section 9.2.1.1 Anonymous block boxes

   [2010-09-29] Percentage values that refer to dimensions of parent boxes
   ignore any intervening anonymous boxes. Add this paragraph:

     [INS: Anonymous block boxes are ignored when resolving percentage
     values that would refer to it: the closest non-anonymous ancestor
     box is used instead. For example, if the child of the anonymous
     block box inside the DIV above needs to know the height of its
     containing block to resolve a percentage height, then it will use
     the height of the containing block formed by the DIV, not of the
     anonymous block box. :INS]

  C.7.29 Section 9.2.1.1 Anonymous block boxes

   [2010-09-29] Clarify the wording:

     When an inline box contains an in-flow block box […] When such an
     inline box is affected by relative positioning, the relative
     positioning also affects the block-level box [INS: contained in the
     block box :INS] .

  C.7.30 Section 9.2.1.1 Anonymous block boxes

   [2010-10-13] Clarify that an inline box that is broken around a
   block-level box is always broken into two pieces, even if one or both
   are empty:

     When an inline box contains an in-flow block-level box, the inline
     box (and its inline ancestors within the same line box) are broken
     around the block-level box[INS: , dividing the inline box into two
     pieces, even if either side is empty. :INS] .

  C.7.31 Section 9.2.2 Inline-level elements and inline boxes

   [2010-08-24] Better define the term “inline-level element/box” and
   define the auxiliary terms “inline box” and “atomic inline-level box.”

  C.7.32 Section 9.2.3 Run-in boxes

   [2010-04-19] Make the definition of 'run-in' more precise:

     [DEL: A run-in box behaves as follows: :DEL]
    1. [DEL: If the run-in box contains a block box, the run-in box
       becomes a block box. :DEL]
    2. [DEL: If a sibling block box (that does not float and is not
       absolutely positioned) follows the run-in box, the run-in box
       becomes the first inline box of the block box. A run-in cannot run
       in to a block that already starts with a run-in or that itself is a
       run-in. :DEL]
    3. [DEL: Otherwise, the run-in box becomes a block box. :DEL]

     [INS: A run-in element (or pseudo-element) A behaves as follows:
     :INS]
    1. [INS: If A has any children that inhibit run-in behavior (see
       below), then A is rendered as if it had 'display: block'. :INS]
    2. [INS: Let B be the first of A's following siblings that is neither
       floating nor absolutely positioned nor has 'display: none'. If B
       exists and has a specified value for 'display' of 'block' or
       'list-item' and is not replaced, then A is rendered as an 'inline'
       element at the start of B's principal box. Note: A is rendered
       before B's ':before' pseudo-element, if any. See 12.1. :INS]
    3. [INS: Otherwise, A is rendered as if it had 'display: block'. :INS]

     [INS: In the above, "siblings" and "children" include both normal
     elements and :before/:after pseudo-elements. :INS]

     [INS: An element or pseudo-element C inhibits run-in behavior if one
     of the following is true. (Note that the definition is recursive.)
     :INS]
    1. [INS: C is not floating and not absolutely positioned and the
       computed value of its 'display' is one of 'block', 'list-item',
       'table' or 'run-in'. :INS]
    2. [INS: C has a computed value for 'display' of 'inline' and it has
       one or more children that inhibit run-in behavior. (Where
       "children" includes both normal elements and :before/:after
       pseudo-elements.) :INS]

   It remains undefined how 'run-in' and ':first-line' interact:

     [INS: It is undefined in CSS 2.1 if a run-in inherits from a
     ':first-line' pseudo-element. :INS]

  C.7.33 Section 9.2.4 The 'display' property

   [2010-08-06] Use the same terminology as in chapter 12:

   list-item
          This value causes an element (e.g., LI in HTML) to generate a
          principal block box and a [DEL: list-item inline :DEL] [INS:
          marker :INS] box.

  C.7.34 Section 9.2.4 The 'display' property

   [2010-08-24] More consistent use of “inline-level.”

   inline-block
          This value causes an element to generate [DEL: a block box,
          which itself is flowed as a single inline box, similar to a
          replaced element :DEL] [INS: an inline-level block container
          :INS] . The inside of an inline-block is formatted as a block
          box, and the element itself is formatted as an [DEL: inline
          replaced element :DEL] [INS: an atomic inline-level box :INS] .

  C.7.35 Section 9.3 Positioning schemes

   [2010-08-24] More consistent use of “inline-level” and “block-level.”

    1. Normal flow. In CSS 2.1, normal flow includes block formatting of
       block[INS: -level :INS] boxes, inline formatting of inline[INS:
       -level :INS] boxes, relative positioning of block[INS: -level :INS]
       [DEL: or :DEL] [INS: and :INS] inline[INS: -level :INS] boxes, and
       [DEL: positioning :DEL] [INS: formatting :INS] of run-in boxes.

  C.7.36 Section 9.4 Normal flow

   [2010-08-24] More consistent use of “inline-level” and “block-level.”

     Boxes in the normal flow belong to a formatting context, which may
     be block or inline, but not both simultaneously. Block[INS: -level
     :INS] boxes participate in a block formatting context. Inline[INS:
     -level :INS] boxes participate in an inline formatting context.

   In 9.4.1:

     Floats, absolutely positioned elements, [DEL: inline-blocks,
     table-cells, table-captions, and elements with 'overflow' other than
     'visible' (except when that value has been propagated to the
     viewport) establish new block formatting contexts :DEL] [INS: block
     containers (such as inline-blocks, table-cells, and table-captions)
     that are not block boxes, and block boxes with 'overflow' other than
     'visible' :INS] .

     In a block formatting context, boxes are laid out one after the
     other, vertically, beginning at the top of a containing block. The
     vertical distance between two sibling boxes is determined by the
     'margin' properties. Vertical margins between adjacent block[INS:
     -level :INS] boxes in a block formatting context collapse.

   In 9.4.2:

     […] When several inline[INS: -level :INS] boxes cannot fit
     horizontally within a single line box, they are distributed among
     two or more vertically-stacked line boxes.

     When the total width of the inline[INS: -level :INS] boxes on a line
     […]is less than the width of the line box containing them, their
     horizontal distribution within the line box is determined by the
     'text-align' property. If that property has the value 'justify', the
     user agent may stretch spaces and words in inline boxes ([DEL:
     except for :DEL] [INS: but not :INS] inline-table and inline-block
     boxes) as well.

  C.7.37 Section 9.3.2 Box offsets: 'top', 'right', 'bottom', 'left'

   [2010-07-19] If 'top', 'right', 'bottom' or 'left' is specified as
   'auto', the used value rather than the computed value is set to the
   negative of the opposite side. For all four, change:

   Computed value: [DEL: for 'position:relative', see section Relative
   Positioning. :DEL] For 'position:static', 'auto'. Otherwise: if
   specified as a length, the corresponding absolute length; if specified
   as a percentage, the specified value; otherwise, 'auto'.

   And in section 9.4.3:

     […] Since boxes are not split or stretched as a result of 'left' or
     'right', the [DEL: computed :DEL] [INS: used :INS] values are
     always: left = -right.

     If both 'left' and 'right' are 'auto' (their initial values), the
     [DEL: computed :DEL] [INS: used :INS] values are '0' (i.e., the
     boxes stay in their original position).

     If 'left' is 'auto', its [DEL: computed :DEL] [INS: used :INS] value
     is minus the value of 'right' (i.e., the boxes move to the left by
     the value of 'right').

     If 'right' is specified as 'auto', its [DEL: computed :DEL] [INS:
     used :INS] value is minus the value of 'left'.

     […] Since boxes are not split or stretched as a result of 'top' or
     'bottom', the [DEL: computed :DEL] [INS: used :INS] values are
     always: top = -bottom. If both are 'auto', their [DEL: computed
     :DEL] [INS: used :INS] values are both '0'. If one of them is
     'auto', it becomes the negative of the other. If neither is 'auto',
     'bottom' is ignored (i.e., the [DEL: computed :DEL] [INS: used :INS]
     value of 'bottom' will be minus the value of 'top').

  C.7.38 Section 9.5 Floats

   [2010-08-24] More consistent use of “inline-level” and “block-level.”

     […] In other words, if inline[INS: -level :INS] boxes are placed on
     the line before a left float is encountered that fits in the
     remaining line box space, the left float is placed on that line,
     aligned with the top of the line box, and then the inline[INS:
     -level :INS] boxes already on the line are moved accordingly to the
     right of the float (the right being the other side of the left
     float) and vice versa for rtl and right floats.

   In 9.5.2:

     Values have the following meanings when applied to non-floating
     block[INS: -level :INS] boxes:

  C.7.39 Section 9.5 Floats

   [2010-10-25] Define exactly what it means for a line box to be next to
   a float:

     […] However, line boxes created next to the float are shortened to
     make room for the margin box of the float.

     [INS: A line box is next to a float when there exists a vertical
     position that satisfies all of these four conditions: (a) at or
     below the top of the line box, (b) at or above the bottom of the
     line box, (c) below the top margin edge of the float, and (d) above
     the bottom margin edge of the float. :INS]

     [INS: Note: this means that floats with zero height or negative
     height do not move line boxes. :INS]

  C.7.40 Section 9.5.2 Controlling flow next to floats: the 'clear' property

   [2010-05-12] Clarify that 'clear' only introduces clearance above an
   element if necessary; and that clearance may have zero height.

  C.7.41 Section 9.5.2 Controlling flow next to floats: the 'clear' property

   [2010-10-13] Added an example of calculating clearance from two
   collapsing margins M1 and M2 and the height H of a float.

  C.7.42 Section 9.5.2 Controlling flow next to floats: the 'clear' property

   [2010-10-13] Clarify the language:

     Computing the clearance of an element on which 'clear' is set is
     done by first determining the hypothetical position of the element's
     top border edge within its parent block. [DEL: This position is
     determined after the top margin of the element has been collapsed
     with previous adjacent margins (including the top margin of the
     parent block). :DEL] [INS: This position where the actual top border
     edge would have been if the element had a non-zero top border and
     its 'clear' property had been 'none'. :INS]

     If this hypothetical position of the element's top border edge is
     not past the relevant floats, then clearance [DEL: must be :DEL]
     [INS: is introduced, and margins collapse according to the rules in
     8.3.1. :INS]

     [INS: Then the amount of clearance is :INS] set to the greater of:
    1. The amount necessary to place the border edge of the block even
       with the bottom outer edge of the lowest float that is to be
       cleared.
    2. [DEL: The amount necessary to make the sum of the following equal
       to the distance to which these margins collapsed when the
       hypothetical position was calculated: :DEL]
          + [DEL: the margins collapsing above the clearance :DEL]
          + [DEL: the clearance itself :DEL]
          + [DEL: if the block's own margins collapse together: the
            block's top margin :DEL]
          + [DEL: if the block's own margins do not collapse together: the
            margins collapsing below the clearance :DEL]
       [INS: The amount necessary to place the top border edge of the
       block at its hypothetical position. :INS]

  C.7.43 Section 9.5.2 Controlling flow next to floats: the 'clear' property

   [2010-10-13] Correction: The hypothetical position is determined by
   assuming the box has a non-zero bottom border (see section 8.3.1):

     This position is where the actual top border edge would have been if
     the element had a non-zero [DEL: top :DEL] [INS: bottom :INS] border
     and its 'clear' property had been 'none'.

  C.7.44 Section 14.2.1 Background properties

   [2010-04-19] 'Fixed' backgrounds in paged media are positioned relative
   to the page box (and thus repeat on every page, just like 'fixed'
   elements). The position of fixed backgrounds in paged media was
   previously undefined.

  C.7.45 Section 9.9.1 Specifying the stack level: the 'z-index' property

   [2010-07-07] Some ambiguities in the description of stacking contexts
   are fixed and the description is clearly marked as non-normative.
   (Appendix E holds the normative description.)

  C.7.46 Section 9.10 Text direction: the 'direction' and 'unicode-bidi'
  properties

   [2010-08-24] More consistent use of “inline-level” and “block-level.”

     User agents that support bidirectional text must apply the Unicode
     bidirectional algorithm to every sequence of inline[INS: -level
     :INS] boxes uninterrupted by a forced line break or block boundary.
     This sequence forms the "paragraph" unit in the bidirectional
     algorithm. The paragraph embedding level is set according to the
     value of the 'direction' property of the containing block rather
     than by the heuristic given in steps P2 and P3 of the Unicode
     algorithm.

     […]

     For the 'direction' property to affect reordering in inline[DEL:
     -level :DEL] elements, the 'unicode-bidi' property's value must be
     'embed' or 'override'.

     […]

   normal
          The element does not open an additional level of embedding with
          respect to the bidirectional algorithm. For inline[DEL: -level
          :DEL] elements, implicit reordering works across element
          boundaries.

   embed
          If the element is inline[DEL: -level :DEL] , this value opens an
          additional level of embedding with respect to the bidirectional
          algorithm. The direction of this embedding level is given by the
          'direction' property. Inside the element, reordering is done
          implicitly. This corresponds to adding a LRE (U+202A; for
          'direction: ltr') or RLE (U+202B; for 'direction: rtl') at the
          start of the element and a PDF (U+202C) at the end of the
          element.

   bidi-override
          For inline[DEL: -level :DEL] elements this creates an override.
          For [DEL: block-level, table-cell, table-caption, or
          inline-block :DEL] [INS: block container :INS] elements this
          creates an override for inline-level descendants not within
          another block container element. This means that inside the
          element, reordering is strictly in sequence according to the
          'direction' property; the implicit part of the bidirectional
          algorithm is ignored. This corresponds to adding a LRO (U+202D;
          for 'direction: ltr') or RLO (U+202E; for 'direction: rtl') at
          the start of the element or at the start of each anonymous child
          block box, if any, and a PDF (U+202C) at the end of the element.

     The final order of characters in each [DEL: block-level element
     :DEL] [INS: block container :INS] is […]

  C.7.47 Section 9.10 Text direction: the 'direction' and 'unicode-bidi'
  properties

   [2010-10-05] Add a reference to bidi class B in Unicode TR 9 to clarify
   what a “forced break” is in the context of the Unicode bidi algorithm:

     […] inline-level boxes uninterrupted by a forced [DEL: line :DEL]
     [INS: (bidi class B) :INS] break or block boundary

  C.7.48 Section 9.10 Text direction: the 'direction' and 'unicode-bidi'
  properties

   [2010-10-25] clarify “non-textual entities”:

     In this process, [DEL: non-textual entities such as images :DEL]
     [INS: replaced elements with 'display: inline' (and replaced
     elements with 'display: run-in', when they generate inline-level
     boxes) :INS] are treated as neutral characters, unless their
     'unicode-bidi' property has a value other than 'normal', in which
     case they are treated as strong characters in the 'direction'
     specified for the element. [INS: All other atomic inline-level boxes
     are treated as neutral characters always. :INS]

  C.7.49 Section 10.1 Definition of "containing block"

   [2010-08-24] More consistent use of “inline-level” and “block-level.”

    1. […]
    2. For other elements, if the element's position is 'relative' or
       'static', the containing block is formed by the content edge of the
       nearest [DEL: block-level, table cell or inline-block :DEL] [INS:
       block container :INS] ancestor box.
    3. […]
    4. […]
         1. In the case that the ancestor is [DEL: inline-level :DEL]
            [INS: an inline box :INS] , the containing block depends on
            the 'direction' property of the ancestor:

  C.7.50 Section 10.2 Content width: the 'width' property

   [2010-05-12] The computed value of 'width' doesn't depend on whether
   the property applies or not:

     Computed value: the percentage or 'auto' as specified or the
     absolute length; [DEL: 'auto' if the property does not apply :DEL]

  C.7.51 Section 10.2 Content width: the 'width' property

   [2010-08-24] More consistent use of “inline-level” and “block-level.”

     This property specifies the content width of boxes [DEL: generated
     by block-level and replaced elements :DEL] .

     This property does not apply to non-replaced inline[DEL: -level
     :DEL] elements.

  C.7.52 Section 10.2 Content width: the 'width' property

   [2010-10-05] Remove unclear and redundant sentence:

     [DEL: The width of a replaced element's box is intrinsic and may be
     scaled by the user agent if the value of this property is different
     than 'auto'. :DEL]

  C.7.53 Section 10.5 Content height: the 'height' property

   [2010-05-12] The computed value of 'height' doesn't depend on whether
   the property applies or not:

     Computed value: the percentage or 'auto' (see prose under
     <percentage>) or the absolute length; [DEL: 'auto' if the property
     does not apply :DEL]

  C.7.54 Section 10.5 Content height: the 'height' property

   [2010-08-24] More consistent use of “inline-level” and “block-level.”

     This property specifies the content height of boxes [DEL: generated
     by block-level, inline-block and replaced elements :DEL] .

     This property does not apply to non-replaced inline[DEL: -level
     :DEL] elements. See the section on computing heights and margins for
     non-replaced inline elements for the rules used instead.

  C.7.55 Section 10.6.7 'Auto' heights for block formatting context roots

   [2010-08-06] Clarify “bottom” and “preceding”:

     In certain cases (see [DEL: the preceding sections :DEL] [INS: e.g.,
     sections 10.6.4 and 10.6.6 :INS] ), the height of an element that
     establishes a block formatting context is computed as follows:

     […]

     In addition, if the element has any floating descendants whose
     bottom margin edge is below the [DEL: bottom :DEL] [INS: the
     element's bottom content edge :INS] , then the height is increased
     to include those edges. Only floats that are children of the element
     itself or of descendants in the normal flow are taken into account,
     e.g., floats inside absolutely positioned descendants or other
     floats are not.

  C.7.56 Section 10.7 Minimum and maximum heights: 'min-height' and 'max-height'

   [2010-10-26] The effect of 'min-height' and 'max-height' on table cells
   is still undefined in CSS:

     [INS: In CSS 2.1, the effect of 'min-height' and 'max-height' on
     tables, inline tables, table cells, table rows, and row groups is
     undefined. :INS]

  C.7.57 Section 10.8 Line height calculations: the 'line-height' and
  'vertical-align' properties

   [2010-06-02] Clarifications to the calculation of the line boxes and
   the minimum line height ("strut"). Item 2 in the bulleted list is
   expanded and items 3 and 4 are merged, as follows:

    1. The height of each inline box in the line box is calculated (see
       "Calculating heights and margins" and the 'line-height' property).
    2. The inline boxes are aligned vertically according to their
       'vertical-align' property. [INS: In case they are aligned 'top' or
       'bottom', they must be aligned so as to minimize the line box
       height. If such boxes are tall enough, there are multiple solutions
       and CSS 2.1 does not define the position of the line box's baseline
       (i.e., the position of the strut, see below). :INS]
    3. The line box height is the distance between the uppermost box top
       and the lowermost box bottom. [INS: (This includes the strut, as
       explained under 'line-height' below.) :INS]
    4. [DEL: If the resulting height is smaller than the minimal height of
       line boxes for this block, as specified by the 'line-height'
       property, the height is increased to be that minimal height. :DEL]

   Furthermore, in 10.8.1, after the definition of “strut,” clarify that
   the font determines the initial baseline:

     [INS: The height and depth of the font above and below the baseline
     are assumed to be metrics that are contained in the font. (For more
     details, see CSS level 3.) :INS]

  C.7.58 Section 10.8 Line height calculations: the 'line-height' and
  'vertical-align' properties

   [2010-08-24] More consistent use of “inline-level” and “block-level.”

     As described in the section on inline formatting contexts, user
     agents flow inline[INS: -level :INS] boxes into a vertical stack of
     line boxes. The height of a line box is determined as follows:
    1. The height of each inline[INS: -level :INS] box in the line box is
       calculated (see "Calculating heights and margins" and the
       'line-height' property).
    2. The inline[INS: -level :INS] boxes are aligned vertically according
       to their 'vertical-align' property.

   In 10.8.1:

     On a [DEL: block-level, table-cell, table-caption or inline-block
     :DEL] [INS: block container :INS] element whose content is composed
     of inline-level elements, 'line-height' specifies the minimal height
     of line boxes within the element. […]

     On an inline[DEL: -level :DEL] element, 'line-height' specifies the
     height that is used in the calculation of the line box height […]

   After the definition of 'vertical-align':

     The following values only have meaning with respect to a parent
     inline[DEL: -level :DEL] element, or to the strut of a parent [DEL:
     block-level, table-cell, table-caption or inline-block :DEL] [INS:
     block container :INS] element.

  C.7.59 Section 10.8.1 Leading and half-leading

   [2010-07-19] Clarify text:

     On a block-level, table-cell, table-caption or inline-block element
     whose content is composed of inline-level elements, 'line-height'
     specifies the minimal height of line boxes within the element. The
     minimum height consists of a minimum height above the [DEL: block's
     :DEL] baseline and a minimum depth below it, exactly as if each line
     box starts with a zero-width inline box with the [DEL: block's :DEL]
     [INS: element's :INS] font and line height properties. [DEL: (what
     TEX calls a "strut"). :DEL] [INS: We call that imaginary box a
     "strut." (The name is inspired by TeX.). :INS]

  C.7.60 Section 10.8.1 Leading and half-leading

   [2010-08-20] Remove text that talks about the “content area” of an
   inline box and about “center vertically” and instead make it more
   explicit how leading is added to a glyph: leading is added above and
   below a hypothetical box around each glyph that represents the (normal
   or ideal) height of a line of text in that font, as given in the font
   metrics.

   Add a note referring to 10.6.1 (which defines that the content area is
   undefined) and explaining that the exact position of backgrounds and
   borders relative to the line box is undefined.

   Also add a note about how to find the relevant metrics in OpenType and
   TrueType fonts.

  C.7.61 Section 10.8.1 Leading and half-leading

   [2010-08-20] Clarify some imprecise terms:

     When an element contains text that is rendered in more than one
     font, user agents may determine the [INS: 'normal' :INS]
     'line-height' value according to the largest font size.

     Generally, when there is only one value of 'line-height' for all
     inline boxes in a [DEL: paragraph :DEL] [INS: block container box
     :INS] (and no [DEL: tall images :DEL] [INS: replaced elements,
     inline-block elements, etc. :INS] ), the above will ensure that
     baselines of successive lines are exactly 'line-height' apart. This
     is important when columns of text in different fonts have to be
     aligned, for example in a table.

  C.7.62 Section 11.1 Overflow and clipping

   [2010-10-25] Clarify which ancestors are meant:

     * A descendant box is positioned absolutely, partly outside the box.
       Such boxes are not always clipped by the overflow property on their
       ancestors; [INS: specifically, they are not clipped by the overflow
       of any ancestor between themselves and their containing block :INS]

  C.7.63 Section 11.1.1 Overflow: the 'overflow' property

   [2010-08-06] The phrase “containing block” in the example doesn't refer
   to the technical term “containing block” but simply to the containing
   box. Change “containing [DEL: block :DEL] ” to “containing [INS: div
   :INS] .”

  C.7.64 Section 11.1.1 Overflow: the 'overflow' property

   [2010-08-24] More consistent use of “inline-level” and “block-level.”

     This property specifies whether content of a [DEL: block-level :DEL]
     [INS: block container :INS] element is clipped when it overflows the
     element's box.

  C.7.65 Section 11.1.1 Overflow: the 'overflow' property

   [2010-10-25] Add missing inline-table:

     Applies to: non-replaced block-level elements, table cells, [INS:
                 inline-table, :INS] and inline-block elements

  C.7.66 Section 11.1.2 Clipping: the 'clip' property

   [2010-10-25] The computed value of 'auto' is 'auto' also when 'auto' is
   specified inside 'rect()':

   Computed value: [DEL: For rectangle values, a rectangle consisting of
   four computed lengths; otherwise, as specified :DEL] [INS: 'auto' if
   specified as 'auto', otherwise a rectangle with four values, each of
   which is 'auto' if specified as 'auto' and the computed length
   otherwise :INS]

   And:

     <top>, <right>, <bottom>, and <left> may either have a <length>
     value or 'auto'. Negative lengths are permitted. The value 'auto'
     means that a given edge of the clipping region will be the same as
     the edge of the element's generated border box (i.e., 'auto' means
     the same as '0' for <top> and <left> (in left-to-right text, <right>
     in right-to-left text), the same as the [DEL: computed :DEL] [INS:
     used :INS] value of the height plus the sum of vertical padding and
     border widths for <bottom>, and the same as the [DEL: computed :DEL]
     [INS: used :INS] value of the width plus the sum of the horizontal
     padding and border widths for <right> (in left-to-right text, <left>
     in right-to-left text), such that four 'auto' values result in the
     clipping region being the same as the element's border box).

  C.7.67 Section 12.5 Lists

   [2010-10-05] Improve wording: the marker box of a list item isn't
   “optional,” it is sometimes absent. Change:

     CSS 2.1 offers basic visual formatting of lists. An element with
     'display: list-item' generates a principal box for the element's
     content [DEL: and an optional marker box :DEL] [INS: and, depending
     on the values of 'list-style-type' and 'list-style-image', possibly
     also a marker box :INS] as a visual indication that the element is a
     list item.

  C.7.68 Section 12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   [2010-07-14] Because of persistent incompatibilites between
   implementations, the constraints on the position of 'outside' markers
   are relaxed in the presence of floats. This will be fixed in a future
   specification.

  C.7.69 Section 12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   [2010-08-06] The 'armenian' list-style-type refers to uppercase
   Armenian numbering.

  C.7.70 Section 12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   [2010-08-06] Define the order of 'inside' marker boxes and ':before'
   pseudo-elements:

   inside
          The marker box is [INS: placed as :INS] the first inline box in
          the principal block box, [DEL: after which the element's content
          flows :DEL] [INS: before the element's content and before any
          :before pseudo-elements :INS] .

  C.7.71 Section 12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   [2010-08-06] CSS 2.1 does not specify the precise location of an
   'outside' marker box, including its z-order. Append:

     CSS 2.1 does not specify the precise location of the marker box
     [INS: or its position in the painting order :INS]

  C.7.72 Section 12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   [2010-11-25] Because of historical ambiguity, CSS level 2 does not yet
   require the marker to be visible when 'list-style-position' is
   'outside' and 'overflow' is other than 'visible'. Insert in the
   definition of 'outside':

     [INS: In CSS 2.1, a UA may hide the marker if the element's
     'overflow' is other than 'visible'. (This is expected to change in
     the future.) :INS]

  C.7.73 Section 13.2 Page boxes: the @page rule

   [2010-07-07] The @page rule can contain not just declarations but also
   other @-rules. (There aren't any such nested @-rules defined in
   level 2, but there are in level 3.)

     An @page rule consists of the keyword "@page", followed by an
     optional page selector, followed by a block [DEL: of declarations
     :DEL] [INS: containing declarations and at-rules :INS] .

     [INS: Note: CSS level 2 has no at-rules that may appear inside
     @page, but such at-rules are expected to be defined in level 3.
     :INS]

   And add just above section 13.2.1:

     [INS: The rules for handling malformed declarations, malformed
     statements, and invalid at-rules inside @page are as defined in
     section 4.2, with the following addition: when the UA expects the
     start of a declaration or at-rule (i.e., an IDENT token or an
     ATKEYWORD token) but finds an unexpected token instead, that token
     is considered to be the first token of a malformed declaration.
     I.e., the rule for malformed declarations, rather than malformed
     statements is used to determine which tokens to ignore in that case.
     :INS]

  C.7.74 Section 13.2.2 Page selectors: selecting left, right, and first pages

   [2010-10-25] Whether the first page of a document is :left or :right
   depends on the major writing direction. Give an example of how:

     All pages are automatically classified by user agents into either
     the :left or :right pseudo-class. [INS: Whether the first page of a
     document is :left or :right depends on the major writing direction
     of the root element. For example, the first page of a document with
     a left-to-right major writing direction would be a :right page, and
     the first page of a document with a right-to-left major writing
     direction would be a :left page. To explicitly force a document to
     begin printing on a left or right page, authors can insert a page
     break before the first generated box. :INS]

   And in 13.3.1:

     [DEL: Whether the first page of a document is :left or :right
     depends on the major writing direction of the document. :DEL]

  C.7.75 Section 13.3.2 Breaks inside elements: 'orphans', 'widows'

   [2010-08-24] More consistent use of “inline-level” and “block-level.”
   Change for both 'orphans' and 'widows':

     Applies to: [DEL: block-level :DEL] [INS: block container :INS]
                 elements

   And change:

     The 'orphans' property specifies the minimum number of lines in a
     block [DEL: element :DEL] [INS: container :INS] that must be left at
     the bottom of a page. The 'widows' property specifies the minimum
     number of lines in a block [DEL: element :DEL] [INS: container :INS]
     that must be left at the top of a page. Examples of how they are
     used to control page breaks are given below.

  C.7.76 Section 13.3.3 Allowed page breaks

   [2010-08-24] More consistent use of “inline-level” and “block-level.”
   Change:

    1. In the vertical margin between block[INS: -level :INS] boxes. […]
    2. Between line boxes inside a block [INS: container :INS] box.
    3. Between the content edge of a block [INS: container :INS] box and
       the outer edges of its child content […]

  C.7.77 Section 15.3 Font family: the 'font-family' property

   [2010-07-19] The specification was ambiguous as to whether parentheses,
   brackets and braces in font names must always be escaped, or only when
   needed to conform to the syntax for declarations. Because of that, and
   because of the many bugs in implementations, all font names must now
   either be quoted, or be escaped so as to consist of only identifiers.

  C.7.78 Section 15.3.1 Generic font families

   [2010-08-26] Make it clearer that CSS does not try to define what fonts
   are serif or sans-serif:

     15.3.1.1 serif

     Glyphs of serif fonts, as the term is used in CSS, [INS: tend to
     :INS] have finishing strokes, flared or tapering ends, or have
     actual serifed endings (including slab serifs). […]

     15.3.1.2 sans-serif

     Glyphs in sans-serif fonts, as the term is used in CSS, [INS: tend
     to :INS] have stroke endings that are plain – [DEL: without any
     :DEL] [INS: with little or no :INS] flaring, cross stroke, or other
     ornamentation. […]

  C.7.79 Section 15.6 Font boldness: the 'font-weight' property

   [2010-04-19] The meaning of the keywords 'bolder' and 'lighter' no
   longer depends on both the inherited weight and the actually used font,
   but only on the inherited weight.

  C.7.80 Section 15.6 Font boldness: the 'font-weight' property

   [2010-10-13] Clarify the algorithm for mapping CSS font weight values
   to the actual weights of a font and make it normative:

     The association of other weights within a family to the numerical
     weight values is intended only to preserve the ordering of darkness
     within that family. However, the following heuristics tell how the
     assignment is done in typical cases:
     * If the font family already uses a numerical scale with nine values
       (like e.g., OpenType does), the font weights should be mapped
       directly.
     * If there is both a face labeled Medium and one labeled Book,
       Regular, Roman or Normal, then the Medium is normally assigned to
       the '500'.
     * The font labeled "Bold" will often correspond to the weight value
       '700'.

     [INS: Once the font family's weights are mapped onto the CSS scale,
     missing weights are selected as follows: :INS]
     * [DEL: If there are fewer then 9 weights in the family, the default
       algorithm for filling the "holes" is as follows. If '500' is
       unassigned, it will be assigned the same font as '400'. If any of
       the values '600', '700', '800' or '900' remains unassigned, they
       are assigned to the same face as the next darker assigned keyword,
       if any, or the next lighter one otherwise. If any of '300', '200'
       or '100' remains unassigned, it is assigned to the next lighter
       assigned keyword, if any, or the next darker otherwise. :DEL]
     * [INS: If the desired weight is less than 400, weights below the
       desired weight are checked in descending order followed by weights
       above the desired weight in ascending order until a match is found.
       :INS]
     * [INS: If the desired weight is greater than 500, weights above
       desired weight are checked in ascending order followed by weights
       below the desired weight in descending order until a match is
       found. :INS]
     * [INS: If the desired weight is 400, 500 is checked first and then
       the rule for desired weights less than 400 is used. :INS]
     * [INS: If the desired weight is 500, 400 is checked first and then
       the rule for desired weights less than 400 is used. :INS]

  C.7.81 Section 15.7 Font size: the 'font-size' property

   [2010-08-06] Changed “Percentages: refer to [DEL: parent element's
   :DEL] font size” to “Percentages: refer to [INS: inherited :INS] font
   size” so that it uses the same terminology as Section 4.3.3.

  C.7.82 Section 16.1 Indentation: the 'text-indent' property

   [2010-08-24] More consistent use of “inline-level” and “block-level.”
   Change:

     Applies to: [DEL: block-level elements, table cells and inline blocks
                 :DEL] [INS: block containers :INS]

     […]

     This property specifies the indentation of the first line of text in
     a block [INS: container :INS] .

  C.7.83 Section 16.1 Indentation: the 'text-indent' property

   [2010-10-25] Clarify that the “first line” of the “first box,” etc., is
   the same as the “first formatted line” of chapter 5:

     [INS: 'Text-indent' only affects a line if it is the first formatted
     line of an element. For example, the first line of an anonymous
     block box is only affected if it is the first child of its parent
     element. :INS]

  C.7.84 Section 16.2 Alignment: the 'text-align' property

   [2010-07-19] The value 'pre-line' of 'white-space' does not inhibit
   justification. (Only lines that end with an explicit newline aren't
   justified, as is the case for any value of 'white-space'.) But,
   'pre-wrap' does inhibit justification. Replace

     [DEL: If the computed value of text-align is 'justify' while the
     computed value of white-space is 'pre' or 'pre-line', the actual
     value of text-align is set to the initial value. :DEL]

   with

     [INS: If an element has a computed value for 'white-space' of 'pre'
     or 'pre-wrap', then neither the glyphs of that element's text
     content nor its white space may be altered for the purpose of
     justification. :INS]

  C.7.85 Section 16.2 Alignment: the 'text-align' property

   [2010-08-24] More consistent use of “inline-level” and “block-level.”
   Change:

     Applies to: [DEL: block-level elements, table cells and inline blocks
                 :DEL] [INS: block containers :INS]

     This property describes how inline[INS: -level :INS] content of a
     block [INS: container :INS] is aligned.

   And:

     […] In the case of 'left', 'right' and 'center', this property
     specifies how the inline[INS: -level :INS] boxes within each line
     box align with respect to the line box's left and right sides;
     alignment is not with respect to the viewport. In the case of
     'justify', this property specifies that the inline[INS: -level :INS]
     boxes are to be made flush with both sides of the block [INS:
     container :INS] if possible, by expanding or contracting the
     contents of inline boxes, else aligned as for the initial value.

  C.7.86 Section 16.3.1 Underlining, overlining, striking, and blinking: the
  'text-decoration' property

   [2010-08-24] Clarify that 'text-decoration' does not propagate to
   inline-table and inline-block elements. Change:

     This property describes decorations that are added to the text of an
     element using the element's color. When specified on [DEL: an inline
     element, it affects all the boxes generated by that element; for all
     other elements, the decorations are propagated to an anonymous
     inline box that wraps all the in-flow inline children of the
     element, and to any block-level in-flow descendants. It is not,
     however, further propagated to floating and absolutely positioned
     descendants, nor to the contents of 'inline-table' and
     'inline-block' descendants. :DEL] [INS: or propagated to an inline
     element, it affects all the boxes generated by that element, and is
     further propagated to any in-flow block-level boxes that split the
     inline (see section 9.2.1.1). For block containers that establish an
     inline formatting context, the decorations are propagated to an
     anonymous inline element that wraps all the in-flow inline-level
     children of the block container. For all other elements it is
     propagated to any in-flow children. Note that text decorations are
     not propagated to floating and absolutely positioned descendants,
     nor to the contents of atomic inline-level descendants such as
     inline blocks and inline tables. :INS]

   and:

     [DEL: If an element contains no text, user agents must refrain from
     rendering these text decorations on the element. For example, images
     will not be underlined. :DEL] [INS: User agents must not render
     these text decorations on content that is not text. For example,
     images and inline blocks must not be underlined. :INS]

  C.7.87 Section 16.3.1 Underlining, overlining, striking, and blinking: the
  'text-decoration' property

   [2010-10-05] CSS 2.1 does not specify if a text decoration that is
   specified on a transparent element ('visibility: hidden') is itself
   transparent, or only transparent where the text is transparent. Add
   this note:

   [INS: Note. If an element E has both 'visibility: hidden' and
   'text-decoration: underline', the underline is invisible (although any
   decoration of E's parent is visible.) However, CSS 2.1 does not specify
   if the underline is visible or invisible in E's children: :INS]
[INS: <span style="visibility: hidden; text-decoration: underline">
 <span style="visibility: visible">
  underlined or not?
 </span>
</span> :INS]

   [INS: This is expected to be specified in level 3 of CSS. :INS]

  C.7.88 Section 16.4 Letter and word spacing: the 'letter-spacing' and
  'word-spacing' properties

   [2010-04-19] Word spacing does not affect fixed-width spaces. Change:

     Word spacing affects each space (U+0020)[DEL: , :DEL] [INS: and
     :INS] non-breaking space (U+00A0) [DEL: and ideographic space
     (U+3000) :DEL] , left in the text after the white space processing
     rules have been applied. [INS: The effect of the property on other
     word-separator characters is undefined. However general punctuation,
     characters with zero advance width (such as the zero with space
     U+200B) and fixed-width spaces (such as U+3000 and U+2000 through
     U+200A) are not affected. :INS]

  C.7.89 Section 16.6 White space: the 'white-space' property

   [2010-10-25] If the document language specifies how newlines are
   represented, those newlines must be passed to the CSS UA as line feed
   (LF) characters. If the document language does not define how newlines
   are expressed (e.g., if text is inserted with the 'content' property),
   the CSS UA must treat CR, and CRLF as if they were LF:

     Newlines in the source can be represented by a carriage return
     (U+000D), a linefeed (U+000A) or both (U+000D U+000A) or by some
     other mechanism that identifies the beginning and end of document
     segments, such as the SGML RECORD-START and RECORD-END tokens. The
     CSS 'white-space' processing model assumes all newlines have been
     normalized to line feeds. [INS: UAs that recognize other newline
     representations must apply the white space processing rules as if
     this normalization has taken place. If no newline rules are
     specified for the document language, each carriage return (U+000D)
     and CRLF sequence (U+000D U+000A) in the document text is treated as
     single line feed character. This default normalization rule also
     applies to generated content. :INS]

     […]
    1. Each tab (U+0009), [DEL: carriage return (U+000D), :DEL] or space
       (U+0020) character surrounding a linefeed (U+000A) character is
       removed if 'white-space' is set to 'normal', 'nowrap', or
       'pre-line'.

  C.7.90 Section 16.6.1 The 'white-space' processing model

   [2010-08-06] The sentence that absolutely positioned elements do not
   create line breaking opportunities is normative, not informative.

  C.7.91 Section 16.6.1 The 'white-space' processing model

   [2010-08-06] The first paragraph is moved to 9.2.2.1. Also, as is clear
   from the latter section, the “should” is a “must”:

     Any text that is directly contained inside a block [INS: container
     :INS] element (not inside an inline element) [DEL: should :DEL]
     [INS: must :INS] be treated as an anonymous inline element.

  C.7.92 Section 16.6.1 The 'white-space' processing model

   [2010-08-24] More consistent use of “inline-level” and “block-level.”
   Change:

     Then, the [DEL: entire block is rendered :DEL] [INS: block
     container's inlines are laid out :INS] .

  C.7.93 Section 17.2 The CSS table model

   [2010-08-04] Clarify that the term “row group” includes header groups
   and footer groups as well:

     Thus, the table model consists of tables, captions, rows, row groups
     [INS: (including header groups and footer groups) :INS] , columns,
     column groups, and cells.

  C.7.94 Section 17.2.1 Anonymous table objects

   [2010-08-24] XML and HTML5, unlike SGML, do not automatically remove
   insignificant white space. Change the rules for generating anonymous
   table elements to suppress most white space between elements, rather
   than consider it the content of an anonymous table cell.

  C.7.95 Section 17.2.1 Anonymous table objects

   [2010-08-24] The static position of absolutely positioned elements
   between table cells or rows was not very useful. Define that the static
   position of such an element is found not just as if the element had
   'position: static', but also had 'display: inline' and zero width and
   height.

  C.7.96 Section 17.4 Tables in the visual formatting model

   [2010-04-19] The caption of the image still describes the image as it
   was in the previous version. Change:

     Diagram of a table with a caption above it[DEL: ; the top margin of
     the caption is collapsed with the top margin of the table :DEL] .

  C.7.97 Section 17.4 Tables in the visual formatting model

   [2010-10-13] Clarify which of the two boxes generated by a table
   element is the principal box:

     In both cases, the table [DEL: box :DEL] generates [DEL: an
     anonymous box :DEL] [INS: a principal block box called the table
     wrapper box :INS] that contains the table box itself and any caption
     boxes (in document order). [INS: The table box is a block-level box
     that contains the table's internal table boxes. :INS] The caption
     boxes are block-level boxes that retain their own content, padding,
     margin, and border areas, and are rendered as normal [DEL: blocks
     :DEL] [INS: block boxes :INS] inside the [DEL: anonymous :DEL] [INS:
     table wrapper :INS] box. Whether the caption boxes are placed before
     or after the table box is decided by the 'caption-side' property, as
     described below.

     The [DEL: anonymous :DEL] [INS: table wrapper :INS] box is a 'block'
     box if the table is block-level, and an 'inline-block' box if the
     table is inline-level. The [DEL: anonymous :DEL] [INS: table wrapper
     :INS] box establishes a block formatting context. The table box (not
     the [DEL: anonymous :DEL] [INS: table wrapper :INS] box) is used
     when doing baseline vertical alignment for an 'inline-table'. The
     width of the [DEL: anonymous :DEL] [INS: table wrapper :INS] box is
     the border-edge width of the table box inside it, as described by
     section 17.5.2. Percentages on 'width' and 'height' on the table are
     relative to the [DEL: anonymous :DEL] [INS: table wrapper :INS]
     box's containing block, not the [DEL: anonymous :DEL] [INS: table
     wrapper :INS] box itself.

     The computed values of properties 'position', 'float', 'margin-*',
     'top', 'right', 'bottom', and 'left' on the table box are used on
     the [DEL: anonymous :DEL] [INS: table wrapper :INS] box instead of
     the table box. The table box uses the initial values for those
     properties.

  C.7.98 Section 17.5.2.2 Automatic table layout

   [2010-10-25] The width of the table caption contributes to the width of
   the table if 'table-layout' is 'auto':

     This gives a maximum and minimum width for each column.

     [INS: The caption width minimum (CAPMIN) is determined by
     calculating for each caption the minimum caption outer width as the
     MCW of a hypothetical table cell that contains the caption formatted
     as "display: block". The greatest of the minimum caption outer
     widths is CAPMIN. :INS]

     Column [INS: and caption :INS] widths influence the final table
     width as follows:
    1. If the 'table' or 'inline-table' element's 'width' property has a
       computed value (W) other than 'auto', the [DEL: property's value as
       used for layout :DEL] [INS: used width :INS] is the greater of
       W[INS: , CAPMIN, :INS] and the minimum width required by all the
       columns plus cell spacing or borders (MIN). If [DEL: W :DEL] [INS:
       the used width :INS] is greater than MIN, the extra width should be
       distributed over the columns.
    2. If the 'table' or 'inline-table' element has 'width: auto', the
       [DEL: table width used for layout :DEL] [INS: used width :INS] is
       the greater of the table's containing block width[INS: , CAPMIN,
       :INS] and MIN. However, if [INS: either CAPMIN or :INS] the maximum
       width required by the columns plus cell spacing or borders (MAX) is
       less than that of the containing block, use [DEL: MAX :DEL] [INS:
       max(MAX, CAPMIN) :INS] .

  C.7.99 Section 17.5.3 Table height algorithms

   [2010-07-15] Clarify that the height of a table row can be influenced
   by 'vertical-align' and 'height', but the content box of the table cell
   is not affected.

     […] it is the maximum of the row's specified 'height', [INS: the
     specified 'height' of each cell in the row, :INS] and the minimum
     height (MIN) required by the cells

   and

     In CSS 2.1, the height of a cell box is the [DEL: maximum of the
     table cell's 'height' property and the minimum height required by
     the content (MIN). :DEL] [INS: minimum height required by the
     content. The table cell's 'height' property can influence the height
     of the row, but it does not increase the height of the cell box.
     :INS] [DEL: A value of 'auto' for 'height' implies that the value
     MIN will be used for layout. :DEL]

  C.7.100 Section 17.5.4 Horizontal alignment in a column

   [2010-08-24] More consistent use of “inline-level.” Change:

     The horizontal alignment of [DEL: a cell's inline content :DEL]
     [INS: inline-level content :INS] within a cell box

  C.7.101 Section B.2 Informative references

   [2010-08-06] BCP 47 replaces RFC 3066.

  C.7.102 Section D. Default style sheet for HTML 4

   [2010-10-05] HTML defines that HTML's block elements represent a
   Unicode embedding even if they are displayed inline by means of a style
   sheet. The default style sheet for HTML didn't yet express that. Add:

html, address,
blockquote,
body, dd, div,
dl, dt, fieldset, form,
frame, frameset,
h1, h2, h3, h4,
h5, h6, noframes,
ol, p, ul, center,
dir, hr, menu, pre   { display: block; [INS: unicode-bidi: embed :INS]  }

  C.7.103 Section E.2 Painting order

   [2010-07-07] Clarification:

     The [DEL: stacking order for :DEL] [INS: painting order for the
     descendants of :INS] an element generating a stacking context (see
     the 'z-index' property) is: […]

  C.7.104 Appendix G Grammar of CSS 2.1

   [2010-10-25] The appendix is not normative.

C.8 Changes since the working draft of 7 December 2010

  C.8.1 8.3.1 Collapsing margins

   The section is completely rewritten to make the normative text shorter
   and clearer.

  C.8.2 10.8.1 Leading and half-leading

   The remark about equal line spacing is made more precise and put in
   green, to make it clearer that it is a note:

     [DEL: Generally, :DEL] [INS: Note. :INS] when there is only one
     value of 'line-height' for all inline boxes in a block container box
     [INS: and they are all in the same font :INS] (and [INS: there are
     :INS] no replaced elements, inline-block elements, etc.), the above
     will ensure that baselines of successive lines are exactly
     'line-height' apart. This is important when columns of text in
     different fonts have to be aligned, for example in a table.

  C.8.3 10.3 Calculating widths and margins

   Added a note that the width calculation only yields a tentative value,
   still to be compared to 'min-width' and 'max-width'

     [INS: Note. The used value of 'width' calculated below is a
     tentative value, and may have to be calculated multiple times,
     depending on 'min-width' and 'max-width', see the section Minimum
     and maximum widths below. :INS]

   A similar note is added to section 10.6 about calculating heights.

  C.8.4 14.3 Gamma correction

   The section on gamma correction was removed. It existed only to help
   implementations on certain operating systems of the 1990s.

  C.8.5 11.1.2 Clipping: the 'clip' property

   The 2nd and 4th offsets of the clip rectangle are offsets from the left
   edge of the element. The 'direction' property no longer has an
   influence.

  C.8.6 9.4.2 Inline formatting contexts

   The words "line feed" were a typing error. The intended words are
   "forced line break."

   (The sentence was subsequently changed further as a result of another
   issue.)

  C.8.7 10.3.2 Inline, replaced elements

   No image formats were found that allow an intrinsic size to be
   expressed as a percentage. The relevant definitions are removed:

     [DEL: Percentage intrinsic widths are first evaluated with respect
     to the containing block's width, if that width does not itself
     depend on the replaced element's width. If it does, then the
     resulting layout is undefined in CSS 2.1. :DEL]

   Similarly in 10.6.2:

     [DEL: Percentage intrinsic heights are evaluated with respect to the
     containing block's height, if that height is specified explicitly,
     or if the replaced element is absolutely positioned. If neither of
     these conditions is met, then percentage values on such replaced
     elements cannot be resolved and such elements are assumed to have no
     intrinsic height. :DEL]

   And in 12.5.1:

     [DEL: 2. If the image's intrinsic width or height is given as a
     percentage, then that percentage is resolved against 1em. :DEL]

  C.8.8 10.1 Definition of "containing block"

   In CSS 2.1, it is undefined what the containing block of an absolutely
   positioned element is, if its nearest positioned ancestor is inline and
   split over multiple lines:

     4. If the element has 'position: absolute' […] following way;
    1. In the case that the ancestor is an [DEL: inline box :DEL] [INS:
       inline-level element :INS] , the containing block [DEL: depends on
       the 'direction' property of the ancestor: :DEL] [INS: is the
       bounding box around the padding boxes of the first and the last
       inline boxes generated for that element. In CSS 2.1, if the inline
       element is split across multiple lines, the containing block is
       undefined. :INS]
         1. [DEL: If the 'direction' is 'ltr', the top and left of the
            containing block are the top and left padding edges of the
            first box generated by the ancestor, and the bottom and right
            are the bottom and right padding edges of the last box of the
            ancestor. :DEL]
         2. [DEL: If the 'direction' is 'rtl', the top and right are the
            top and right padding edges of the first box generated by the
            ancestor, and the bottom and left are the bottom and left
            padding edges of the last box of the ancestor. :DEL]
       [DEL: Note: This may cause the containing block's width to be
       negative. :DEL]

  C.8.9 13.2.2 Page selectors: selecting left, right, and first pages

   CSS 2.1 does not define if ':first' applies to the first page or the
   first non-blank page:

     [INS: If a forced break occurs before the first generated box, it is
     undefined in CSS 2.1 whether ':first' applies to the blank page
     before the break or to the page after it. :INS]

  C.8.10 8.3.1 Collapsing margins

   Added a note with a link to 9.4.2, which defines types of line boxes
   that exist but do not interfere with collapsing margins.

     * no line boxes, no clearance, no padding and no border separate them
       [INS: (Note that certain zero-height line boxes (see 9.4.2) are
       ignored for this purpose.) :INS]

  C.8.11 10.8 Line height calculations: the 'line-height' and 'vertical-align'
  properties

   The definition of which height is used for the different kinds of
   inline-level boxes is made explicit, rather than linked:

    1. The height of each inline-level box in the line box is calculated.
       [INS: For replaced elements, inline-block elements, and
       inline-table elements, this is the height of their margin box; for
       inline boxes, this is their 'line-height'. :INS] (See "Calculating
       heights and margins" and the [DEL: 'line-height' property :DEL]
       [INS: height of inline boxes in "Leading and half-leading" :INS] .)

   The part of the definition that was in 10.6.2 is removed:

     [DEL: For 'inline' and 'inline-block' elements, the margin box is
     used when calculating the height of the line box. :DEL]

  C.8.12 10.8.1 Leading and half-leading

   Inserted the following before the definitions of the keywords of
   'vertical-align' to define precisely which box is aligned:

     [INS: In the following definitions, for inline non-replaced
     elements, the box used for alignment is the box whose height is the
     'line-height' (containing the box's glyphs and the half-leading on
     each side, see above). For all other elements, the box used for
     alignment is the margin box. :INS]

   Also, to make sure there always is a box whose height is 'line-height',
   a phrase earlier in the same section was removed:

     User agent must align the glyphs in a non-replaced inline box to
     each other by their relevant baselines[DEL: , and to nested inline
     boxes according to 'vertical-align' :DEL] .

   And another modified:

     The height of the inline box [DEL: is then the smallest such that it
     encloses all glyphs and their leading, as well as all nested inline
     boxes. :DEL] [INS: encloses all glyphs and their half-leading on
     each side and is thus exactly 'line-height'. Boxes of child elements
     do not influence this height. :INS]

  C.8.13 10.6.1 Inline, non-replaced elements

   Improve language:

     The vertical padding, border and margin of an inline, non-replaced
     box start at the top and bottom of the content area, [DEL: not :DEL]
     [INS: and has nothing to do with :INS] the 'line-height'. But only
     the 'line-height' is used when calculating the height of the line
     box.

  C.8.14 9.5.1 Positioning the float: the 'float' property

   A left float must not only not overlap a right float, but must also not
   be completely to the right of it.

     3. The right outer edge of a left-floating box may not be to the
     right of the left outer edge of any right-floating box that is [DEL:
     to the right of :DEL] [INS: next to :INS] it. Analogous rules hold
     for right-floating elements.

  C.8.15 9.2.1.1 Anonymous block boxes

   An error in the description of the example:

     The resulting boxes would be [DEL: an anonymous block box around
     :DEL] [INS: a block box representing :INS] the BODY, containing an
     anonymous block box around C1, the SPAN block box, and another
     anonymous block box around C2.

  C.8.16 5.12.1 The :first-line pseudo-element

   UAs are not required to support 'vertical-align' on '::first-line'.

     The following properties apply to a :first-line pseudo-element: font
     properties, color property, background properties, 'word-spacing',
     'letter-spacing', 'text-decoration', [DEL: 'vertical-align', :DEL]
     'text-transform', [INS: and :INS] 'line-height'. UAs may apply other
     properties as well.

  C.8.17 16.6 White space: the 'white-space' property

   CSS 2.1 does not define whether the Line Separator character in Unicode
   and other forced line break characters (other than LF) cause a line
   break. (Level 3 will probably define this in detail.)

   pre
          This value prevents user agents from collapsing sequences of
          white space. Lines are only broken at [DEL: newlines in the
          source, or at occurrences of "\A" in generated content :DEL]
          [INS: preserved newline characters :INS] .

   and

   pre-wrap
          This value prevents user agents from collapsing sequences of
          white space. Lines are broken at [DEL: newlines in the source,
          at occurrences of "\A" in generated content, :DEL] [INS:
          preserved newline characters, :INS] and as necessary to fill
          line boxes.

   pre-line
          This value directs user agents to collapse sequences of white
          space. Lines are broken at [DEL: newlines in the source, at
          occurrences of "\A" in generated content, :DEL] [INS: preserved
          newline characters, :INS] and as necessary to fill line boxes.

   and add this paragraph:

     [INS: UAs must recognize line feeds (U+000A) as newline characters.
     UAs may additionally treat other forced break characters as newline
     characters per UAX14. :INS]

  C.8.18 12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   CSS 2.1 omits to define how the implicit counters of 'list-item' are
   reset and incremented. This will be specified in level 3.

     [INS: CSS 2.1 does not define how the list numbering is reset and
     incremented. This is expected to be defined in the CSS List Module
     [CSS3LIST]. :INS]

  C.8.19 9.7 Relationships between 'display', 'position', and 'float'

   Some UAs treat 'display: list-item' on the root element as 'block'.
   Allow that behavior for now:

     4. Otherwise, if the element is the root element, 'display' is set
     according to the table below[INS: , except that it is undefined in
     CSS 2.1 whether a specified value of 'list-item' becomes a computed
     value of 'block' or 'list-item' :INS] .

  C.8.20 9.4.2 Inline formatting contexts

   Empty line boxes aren't generated at all, rather than just ignored for
   margin collapsing. But their virtual position must still be calculated
   if they contain empty inlines with absolutely positioned or floating
   descendants:

     [INS: Line boxes are created as needed to hold inline-level content
     within an inline formatting context. :INS] Line boxes that contain
     no text, no preserved white space, no inline elements with non-zero
     margins, padding, or borders, and no other in-flow content (such as
     images, inline blocks or inline tables), and do not end with a [DEL:
     line feed :DEL] [INS: preserved newline :INS] must be treated as
     zero-height line boxes [INS: for the purposes of determining the
     positions of any elements inside of them, and treated as not
     existing for any other purpose. :INS] [DEL: For the purposes of
     margin collapsing, this line box must be ignored. :DEL]

  C.8.21 4.1.9 Comments

   Use same phrasing for comment tokens as in section 4.1.1:

     They may occur anywhere [DEL: between :DEL] [INS: outside other
     :INS] tokens

  C.8.22 12.5.1 Lists: the 'list-style-type', 'list-style-image',
  'list-style-position', and 'list-style' properties

   The size computation of list marker images without an intrinsic size is
   modified to be consistent with how image sizes are computed in other
   places, using 1em for the available width and 1:1 for the default
   aspect ratio:

    1. [DEL: If the image has an intrinsic width or height, then that
       intrinsic width/height becomes the image's used width/height. :DEL]
       [INS: If the image has a intrinsic width and height, the used width
       and height are the intrinsic width and height. :INS]
    2. [DEL: If the image has no intrinsic ratio and a ratio cannot be
       calculated from its width and height, then its intrinsic ratio is
       assumed to be 1:1. :DEL] [INS: Otherwise, if the image has an
       intrinsic ratio and either an intrinsic width or an intrinsic
       height, the used width/height is the same as the provided intrinsic
       width/height, and the used value of the missing dimension is
       calculated from the provided dimension and the ratio. :INS]
    3. [DEL: If the image has a width but no height, its height is
       calculated from the intrinsic ratio. :DEL] [INS: Otherwise, if the
       image has an intrinsic ratio, the used width is 1em and the used
       height is calculated from this width and the intrinsic ratio. If
       this would produce a height larger than 1em, then the used height
       is instead set to 1em and the used width is calculated from this
       height and the intrinsic ratio. :INS]
    4. [DEL: If the image's height cannot be resolved from the rules
       above, then the image's height is assumed to be 1em. :DEL] [INS:
       Otherwise, the image's used width is its intrinsic width if it has
       one, or else 1em. The image's used height is its intrinsic height
       if it has one, or else 1em. :INS]
    5. [DEL: If the image has no intrinsic width, then its width is
       calculated from the resolved height and the intrinsic ratio. :DEL]

  C.8.23 9.5.1 Positioning the float: the 'float' property

   Because of lack of sufficient implementations, the top of a floating
   box is allowed to be above the top of earlier boxes in certain
   difficult cases. Add after the numbered list:

     [INS: But in CSS 2.1, if, within the block formatting context, there
     is an in-flow negative vertical margin such that the float's
     position is above the position it would be at were all such negative
     margins set to zero, the position of the float is undefined. :INS]

  C.8.24 9.3 Positioning schemes

   Add formal definitions of the terms “out of flow,” “in-flow” and “flow
   of an element”:

     [INS: An element is called out of flow if it is floated, absolutely
     positioned, or is the root element. An element is called in-flow if
     it is not out-of-flow. The flow of an element A is the set
     consisting of A and all in-flow elements whose nearest out-of-flow
     ancestor is A. :INS]

  C.8.25 9.10 Text direction: the 'direction' and 'unicode-bidi' properties

   The list of features affected by 'direction' is not meant to be
   exclusive:

     This property specifies the base writing direction of blocks and the
     direction of embeddings and overrides (see 'unicode-bidi') for the
     Unicode bidirectional algorithm. In addition, it specifies [INS:
     such things as :INS] the direction of table column layout, the
     direction of horizontal overflow, the position of an incomplete last
     line in a block in case of 'text-align: justify'.

  C.8.26 16.3.1 Underlining, overlining, striking, and blinking: the
  'text-decoration' property

   Whether the effect of 'text-decoration' propagates into tables may be
   the subject of a separate property in level 3:

     […] When specified on or propagated to an inline element, it affects
     all the boxes generated by that element, and is further propagated
     to any in-flow block-level boxes that split the inline (see
     section 9.2.1.1). [INS: But, in CSS 2.1, it is undefined whether the
     decoration propagates into block-level tables. :INS]

  C.8.27 16.3.1 Underlining, overlining, striking, and blinking: the
  'text-decoration' property

   Clarify that the text for 'inset' and 'outset' only talks about how the
   border styles look (and not, e.g., about which style takes priority):

   *inset
          In the separated borders model, the border makes the entire box
          look as though it were embedded in the canvas. In the collapsing
          border model, [INS: drawn the :INS] same as 'ridge'.

   *outset
          In the separated borders model, the border makes the entire box
          look as though it were coming out of the canvas. In the
          collapsing border model, [INS: drawn the :INS] same as 'groove'.

  C.8.28 10.4 Minimum and maximum widths: 'min-width' and 'max-width'

   Added:

     [INS: In CSS 2.1, the effect of 'min-width' and 'max-width' on
     tables, inline tables, table cells, table columns, and column groups
     is undefined. :INS]

  C.8.29 9.3.2 Box offsets: 'top', 'right', 'bottom', 'left'

   'Top', right', 'bottom' and 'left' are always computed, independent of
   the value of other properties:

   'top'

   Value:   <length> | <percentage> | auto | inherit
   Initial:   auto
   Applies to:   positioned elements
   Inherited:   no
   Percentages:   refer to height of containing block
   Media:   visual
   Computed value:   [DEL: for 'position:static', 'auto'. Otherwise: :DEL]
   if specified as a length, the corresponding absolute length; if
   specified as a percentage, the specified value; otherwise, 'auto'.

   Analogously for 'right', 'bottom' and 'left'.

  C.8.30 9.2.1.1 Anonymous block boxes

   Clarify that the two parts of an inline that is split by a block are on
   opposite sides of the block:

     When an inline box contains an in-flow block-level box, the inline
     box (and its inline ancestors within the same line box) are broken
     around the block-level box (and any block-level siblings that are
     consecutive or separated only by collapsible whitespace and/or
     out-of-flow elements), [DEL: dividing :DEL] [INS: splitting :INS]
     the inline box into two pieces (even if either side is empty)[INS: ,
     one on each side of the block-level box(es) :INS] .

  C.8.31 17.4 Tables in the visual formatting model

   More precise rule for which properties apply to the table box and which
   to the table wrapper box:

     The computed values of properties 'position', 'float', 'margin-*',
     'top', 'right', 'bottom', and 'left' on the table [DEL: box :DEL]
     [INS: element :INS] are used on the table wrapper box [DEL: instead
     of :DEL] [INS: and not :INS] the table box[DEL: . The table box uses
     the initial values for those properties. :DEL] [INS: ; all other
     values of non-inheritable properties are used on the table box and
     not the table wrapper box. (Where the table element's values are not
     used on the table and table wrapper boxes, the initial values are
     used instead.) :INS]

  C.8.32 11.1.2 Clipping: the 'clip' property

   Some text and arrows were added to the example to make it easier to see
   where the four offsets of the clip rectangle are applied:

   Two clipping regions    [D]

  C.8.33 13.2 Page boxes: the @page rule

   The definition of the @page rule didn't mention explicitly (except with
   examples) that white space is allowed:

     An @page rule consists of the keyword "@page", followed by an
     optional page selector, followed by a block containing declarations
     and at-rules. [INS: Comments and white space are allowed, but
     optional, between the @page token and the page selector and between
     the page selector and the block. :INS]

  C.8.34 4.1.1 Tokenization

   Added an example to illustrate what is meant by “the longest match” in
   the tokenizer:

   Example(s):

   [INS: For example, the rule of the longest match means that "red-->" is
   tokenized as the IDENT "red--" followed by the DELIM ">", rather than
   as an IDENT followed by a CDC. :INS]

  C.8.35 4.2 Rules for handling parsing errors

   Clarify that “end of line” means an end of line character, i.e., the
   end of file is not an end of line:

     User agents must close strings upon reaching the end of a line [INS:
     (i.e., before an unescaped line feed, carriage return or form feed
     character) :INS] , but then drop the construct (declaration or rule)
     in which the string was found.

  C.8.36 3.1 Definitions

   There may soon be a newer version of HTML then HTML4:

     An HTML user agent is one that supports [INS: one or more of :INS]
     the HTML [DEL: 2.x, HTML 3.x, or HTML 4.x :DEL] specifications. A
     user agent that supports XHTML [XHTML], but not HTML [DEL: (as
     listed in the previous sentence) :DEL] is not considered an HTML
     user agent for the purpose of conformance with this specification.

  C.8.37 4.3.4 URLs and URIs

   Make the note about parsing URLs shorter and clearer:

   Note that COMMENT tokens cannot occur within other tokens: thus,
   "url(/*x*/pic.png)" denotes the URI "/*x*/pic.png", not "pic.png".

  C.8.38 9.5 Floats

   Clarify the note:

     Note: this means that floats with zero [INS: outer :INS] height or
     negative [INS: outer :INS] height do not shorten line boxes.

  C.8.39 11.1.1 Overflow: the 'overflow' property

   Shorten the “applies to” line:

   'overflow'

   Value:   visible | hidden | scroll | auto | inherit
   Initial:   visible
   Applies to:   [DEL: non-replaced block-level elements, table cells,
   inline-table, and inline-block elements :DEL] [INS: block containers
   :INS]
   Inherited:   no
   Percentages:   N/A
   Media:   visual
   Computed value:   as specified

  C.8.40 9.2.1.1 Anonymous block boxes

   Clarify how block-level elements inside inline elements are affected by
   relative positioning:

     When such an inline box is affected by relative positioning, [DEL:
     the relative positioning :DEL] [INS: any resulting translation :INS]
     also affects the block-level box contained in the inline box.

  C.8.41 16.2 Alignment: the 'text-align' property

   Text is justified within the line box, which may be narrower than the
   block box:

     In the case of 'justify', this property specifies that the
     inline-level boxes are to be made flush with both sides of the [DEL:
     block container :DEL] [INS: line box :INS] if possible, […]

  C.8.42 9.5 Floats

   Only the current and later line boxes can be shortened by a float.
   Earlier line boxes, if the float ends up next to them, will overlap the
   float instead:

     Since a float is not in the flow, non-positioned block boxes created
     before and after the float box flow vertically as if the float did
     not exist. However, [INS: the current and subsequent :INS] line
     boxes created next to the float are shortened to make room for the
     margin box of the float.

  C.8.43 9.4.2 Inline formatting contexts

   A float may cause a gap between line boxes:

     […] Thus, a paragraph is a vertical stack of line boxes. Line boxes
     are stacked with no vertical separation [INS: (except as specified
     elsewhere) :INS] and they never overlap.

  C.8.44 5.12 Pseudo-elements

   Added a note to make it explicit that CSS 2.1 does not define
   ':first-line' and ':first-letter' completely:

     [INS: Note that the sections below do not define the exact rendering
     of ':first-line' and ':first-letter' in all cases. A future level of
     CSS may define them more precisely. :INS]

  C.8.45 9.5 Floats

   Clarify that “overlap a float” means overlap the margin box of the
   float:

     The border box of a table, a block-level replaced element, or an
     element in the normal flow that establishes a new block formatting
     context (such as an element with 'overflow' other than 'visible')
     must not overlap [INS: the margin box of :INS] any floats in the
     same block formatting context as the element itself.

  C.8.46 9.5 Floats

   A line box next to a float is not shortened if it already doesn't
   overlap the float:

     […] However, the current and subsequent line boxes created next to
     the float are shortened [INS: as necessary :INS] to make room for
     the margin box of the float.

  C.8.47 14.2.1 Background properties: 'background-color', 'background-image',
  'background-repeat', 'background-attachment', 'background-position', and
  'background'

   Because of insufficient implementations of background images with an
   intrinsic ratio but no intrinsic size, add this note:

     [INS: However, the position is undefined in CSS 2.1 if the image has
     an intrinsic ratio, but no intrinsic size. :INS]

  C.8.48 9.2.4 The 'display' property

   Because some aspects of 'run-in' (most notably if and how 'clear'
   should apply to run-in elements when they are inline) are still under
   discussion, 'run-in' has been reclassified as a level 3 feature.

   Change in section 9.2.4:

  Value: inline | block | list-item | [DEL: run-in | :DEL] inline-block |
         table | inline-table | inline | block | list-item | run-in |
         inline-block | table | inline-table | table-row-group |
         table-header-group | table-footer-group | table-row |
         table-column-group | table-column | table-cell | table-caption | none |
         inherit

   and

   [DEL: run-in :DEL]
          [DEL: This value creates either block or inline boxes, depending
          on context. Properties apply to run-in boxes based on their
          final status (inline-level or block-level). :DEL]

   Remove 'run-in' from section 9.2.1 “Block-level elements and block
   boxes”:

     […] The following values of the 'display' property make an element
     block-level: 'block', 'list-item', [DEL: and 'run-in' (part of the
     time; see run-in boxes), :DEL] and 'table'.

   Remove 'run-in' from section 9.2.2 “Inline-level elements and inline
   boxes”:

     […] The following values of the 'display' property make an element
     inline-level: 'inline', 'inline-table', [INS: and :INS]
     'inline-block' [DEL: and 'run-in' (part of the time; see run-in
     boxes) :DEL] . […]

     […] A non-replaced element with a 'display' value of 'inline'
     generates an inline box. [DEL: An element with a 'display' value of
     'run-in' can also generate an inline box; see run-in boxes. :DEL]

   Replace section 9.2.3 “Run-in boxes” by this:

     9.2.3 Run-in boxes

     [This section exists so that the section numbers are the same as in
     previous drafts. 'Display: run-in' is now defined in CSS level 3
     (see CSS basic box model).]

   Remove 'run-in' from section 9.3 “Positioning schemes”:

    1. Normal flow. In CSS 2.1, normal flow includes block formatting of
       block-level boxes, inline formatting of inline-level boxes, [INS:
       and :INS] relative positioning of block-level and inline-level
       boxes[DEL: , and formatting of run-in boxes :DEL] .

   Remove 'run-in' from section 9.5.2 “Controlling flow next to floats:
   the 'clear' property”:

     [DEL: For run-in boxes, this property applies to the final block box
     to which the run-in box belongs. :DEL]

   Remove 'run-in' from section 9.7 “Relationships between 'display',
   'position', and 'float'”:

   Specified value Computed value
   inline-table table
   inline, [DEL: run-in, :DEL] table-row-group, table-column,
   table-column-group, table-header-group, table-footer-group, table-row,
   table-cell, table-caption, inline-block block
   others same as specified

   Remove 'run-in' from section 9.10 “Text direction: the 'direction' and
   'unicode-bidi' properties”:

     The final order of characters in each block container is the same as
     if the bidi control codes had been added as described above, markup
     had been stripped, and the resulting character sequence had been
     passed to an implementation of the Unicode bidirectional algorithm
     for plain text that produced the same line-breaks as the styled
     text. In this process, replaced elements with 'display: inline'
     [DEL: (and replaced elements with 'display: run-in', when they
     generate inline-level boxes) :DEL] are treated as neutral
     characters, unless their 'unicode-bidi' property has a value other
     than 'normal', in which case they are treated as strong characters
     in the 'direction' specified for the element. All other atomic
     inline-level boxes are treated as neutral characters always.

   Remove 'run-in' from section E.1 “Definitions”:

   Tree Order
          Preorder depth-first traversal of the rendering tree, in logical
          (not visual) order for bidirectional content, after taking into
          account properties that move boxes around [DEL: such as the
          'run-in' value of 'display' :DEL] .

   Remove 'run-in' from section 12.1 “The :before and :after
   pseudo-elements”:

     The :before and :after pseudo-elements interact with other
     boxes[DEL: , such as run-in boxes, :DEL] as if they were real
     elements inserted just inside their associated element.

   and also from the subsequent example.

  C.8.49 6.1.2 Computed values

   Clarify that the keyword 'inherit' means that the specified value is
   the inherited value. The value is not the keyword itself.

     [DEL: When the specified value is not 'inherit', :DEL] the computed
     value of a property is determined as specified by the Computed Value
     line in the definition of the property. See the section on
     inheritance for the definition of computed values when the specified
     value is 'inherit'.

   And in 6.2.1:

     Each property may also have a [DEL: specified :DEL] [INS: cascaded
     :INS] value of 'inherit', which means that, for a given element, the
     property takes the same [DEL: computed :DEL] [INS: specified :INS]
     value as the property for the element's parent. The 'inherit' value
     can be used to [DEL: strengthen inherited :DEL] [INS: enforce
     inheritance of :INS] values, and it can also be used on properties
     that are not normally inherited.

  C.8.50 10.3.2 Inline, replaced elements

   Because of lack of implementations, the width of a replaced element
   with an intrinsic ratio but neither intrinsic with nor intrinsic height
   is left undefined:

     If 'height' and 'width' both have computed values of 'auto' and the
     element has an intrinsic ratio but no intrinsic height or width,
     [DEL: and :DEL] [INS: then the used value of 'width' is undefined in
     CSS 2.1. However, it is suggested that, if :INS] the containing
     block's width does not itself depend on the replaced element's
     width, then the used value of 'width' is calculated from the
     constraint equation used for block-level, non-replaced elements in
     normal flow.

  C.8.51 Section 9.5.2 Controlling flow next to floats: the 'clear' property

   Because of lack of implementations, also allow 'clear' to work in a
   different way for now:

     Computing the clearance of an element on which 'clear' is set is
     done by first determining the hypothetical position of the element's
     top border edge [DEL: within its parent block :DEL] . This position
     is where the actual top border edge would have been if the element
     had a non-zero bottom border and its 'clear' property had been
     'none'.

     If this hypothetical position of the element's top border edge is
     not past the relevant floats, then clearance is introduced, and
     margins collapse according to the rules in 8.3.1.

     Then the amount of clearance is set to the greater of:
    1. The amount necessary to place the border edge of the block even
       with the bottom outer edge of the lowest float that is to be
       cleared.
    2. The amount necessary to place the top border edge of the block at
       its hypothetical position.

     [INS: Alternatively, clearance is set exactly to the amount
     necessary to place the border edge of the block even with the bottom
     outer edge of the lowest float that is to be cleared. :INS]

     [INS: Note: Both behaviors are allowed pending evaluation of their
     compatibility with existing Web content. A future CSS specification
     will require either one or the other. :INS]

  C.8.52 G.2 Lexical scanner

   The tokenizer in the appendix allowed backslashes in the URI token, in
   contradiction with the same token in the core grammar and the error
   recovery token {baduri}:

[DEL: {U}{R}{L}"("{w}{string}{w}")"      {return URI;} :DEL]
[DEL: {U}{R}{L}"("{w}{url}{w}")"         {return URI;} :DEL]
[INS: "url("{w}{string}{w}")"            {return URI;} :INS]
[INS: "url("{w}{url}{w}")"               {return URI;} :INS]

  C.8.53 Section 9.5.2 Controlling flow next to floats: the 'clear' property

   The top border edge is now well-defined in the section on collapsing
   margins. That is the hypothetical position to use for clearance:

     This position is where the actual top border edge would have been if
     the element [DEL: had a non-zero bottom border and its :DEL] [INS:
     's :INS] 'clear' property had been 'none'.

  C.8.54 9.5 Floats

   Remove ambiguities:

     If a shortened line box is too small to contain any content [DEL:
     after the float :DEL] , then [DEL: that content :DEL] [INS: the line
     box :INS] is shifted downward [INS: (and its width recomputed) :INS]
     until either [DEL: it :DEL] [INS: some content :INS] fits or there
     are no more floats present. Any content in the current line before a
     floated box is reflowed in the [DEL: first available :DEL] [INS:
     same :INS] line on the other side of the float.

  C.8.55 10.6.3 Block-level non-replaced elements in normal flow when 'overflow'
  computes to 'visible'

   Removed redundancy (the top edge was already defined elsewhere) and
   made the implied cases for the bottom edge explicit:

     [DEL: If it only has inline-level children, the height is the
     distance between the top of the topmost line box and the bottom of
     the bottommost line box. :DEL]

     [DEL: If it has block-level children, the height is the distance
     between the top border-edge of the topmost block-level child box
     that does not have margins collapsed through it and the bottom
     border-edge of the bottommost block-level child box that does not
     have margins collapsed through it. However, if the element has a
     non-zero top padding and/or top border, or is the root element, then
     the content starts at the top margin edge of the topmost child. (The
     first case expresses the fact that the top and bottom margins of the
     element collapse with those of the topmost and bottommost children,
     while in the second case the presence of the padding/border prevents
     the top margins from collapsing.) Similarly, if the bottom margin of
     the block does not collapse with the bottom margin of its last
     in-flow child, then the content ends at the bottom margin edge of
     the bottommost child. :DEL]

     [INS: The element's height is the distance from its top content edge
     to the first applicable of the following: :INS]
    1. [INS: the bottom edge of the last line box, if the box establishes
       a inline formatting context with one or more lines :INS]
    2. [INS: the bottom edge of the bottom (possibly collapsed) margin of
       its last in-flow child, if the child's bottom margin does not
       collapse with the element's bottom margin :INS]
    3. [INS: the bottom border edge of the last in-flow child whose top
       margin doesn't collapse with the element's bottom margin :INS]
    4. [INS: zero, otherwise :INS]

                   Appendix D. Default style sheet for HTML 4

   This appendix is informative, not normative.

   This style sheet describes the typical formatting of all HTML 4
   ([HTML4]) elements based on extensive research into current UA
   practice. Developers are encouraged to use it as a default style sheet
   in their implementations.

   The full presentation of some HTML elements cannot be expressed in
   CSS 2.1, including replaced elements ("img", "object"), scripting
   elements ("script", "applet"), form control elements, and frame
   elements.

   For other elements, the legacy presentation can be described in CSS but
   the solution removes the element. For example, the FONT element can be
   replaced by attaching CSS declarations to other elements (e.g., DIV).
   Likewise, legacy presentation of presentational attributes (e.g., the
   "border" attribute on TABLE) can be described in CSS, but the markup in
   the source document must be changed.
html, address,
blockquote,
body, dd, div,
dl, dt, fieldset, form,
frame, frameset,
h1, h2, h3, h4,
h5, h6, noframes,
ol, p, ul, center,
dir, hr, menu, pre   { display: block; unicode-bidi: embed }
li              { display: list-item }
head            { display: none }
table           { display: table }
tr              { display: table-row }
thead           { display: table-header-group }
tbody           { display: table-row-group }
tfoot           { display: table-footer-group }
col             { display: table-column }
colgroup        { display: table-column-group }
td, th          { display: table-cell }
caption         { display: table-caption }
th              { font-weight: bolder; text-align: center }
caption         { text-align: center }
body            { margin: 8px }
h1              { font-size: 2em; margin: .67em 0 }
h2              { font-size: 1.5em; margin: .75em 0 }
h3              { font-size: 1.17em; margin: .83em 0 }
h4, p,
blockquote, ul,
fieldset, form,
ol, dl, dir,
menu            { margin: 1.12em 0 }
h5              { font-size: .83em; margin: 1.5em 0 }
h6              { font-size: .75em; margin: 1.67em 0 }
h1, h2, h3, h4,
h5, h6, b,
strong          { font-weight: bolder }
blockquote      { margin-left: 40px; margin-right: 40px }
i, cite, em,
var, address    { font-style: italic }
pre, tt, code,
kbd, samp       { font-family: monospace }
pre             { white-space: pre }
button, textarea,
input, select   { display: inline-block }
big             { font-size: 1.17em }
small, sub, sup { font-size: .83em }
sub             { vertical-align: sub }
sup             { vertical-align: super }
table           { border-spacing: 2px; }
thead, tbody,
tfoot           { vertical-align: middle }
td, th, tr      { vertical-align: inherit }
s, strike, del  { text-decoration: line-through }
hr              { border: 1px inset }
ol, ul, dir,
menu, dd        { margin-left: 40px }
ol              { list-style-type: decimal }
ol ul, ul ol,
ul ul, ol ol    { margin-top: 0; margin-bottom: 0 }
u, ins          { text-decoration: underline }
br:before       { content: "\A"; white-space: pre-line }
center          { text-align: center }
:link, :visited { text-decoration: underline }
:focus          { outline: thin dotted invert }

/* Begin bidirectionality settings (do not change) */
BDO[DIR="ltr"]  { direction: ltr; unicode-bidi: bidi-override }
BDO[DIR="rtl"]  { direction: rtl; unicode-bidi: bidi-override }

*[DIR="ltr"]    { direction: ltr; unicode-bidi: embed }
*[DIR="rtl"]    { direction: rtl; unicode-bidi: embed }

@media print {
  h1            { page-break-before: always }
  h1, h2, h3,
  h4, h5, h6    { page-break-after: avoid }
  ul, ol, dl    { page-break-before: avoid }
}



             Appendix E. Elaborate description of Stacking Contexts

   Contents
     * E.1 Definitions
     * E.2 Painting order
     * E.3 Notes

   This chapter defines the CSS 2.1 painting order in more detail than
   described in the rest of the specification.

E.1 Definitions

   Tree Order
          Preorder depth-first traversal of the rendering tree, in logical
          (not visual) order for bidirectional content, after taking into
          account properties that move boxes around.

   Element
          In this description, "element" refers to actual elements,
          pseudo-elements, and anonymous boxes. Pseudo-elements and
          anonymous boxes are treated as descendants in the appropriate
          places. For example, an outside list marker comes before an
          adjoining ':before' box in the line box, which comes before the
          content of the box, and so forth.

E.2 Painting order

   The bottom of the stack is the furthest from the user, the top of the
   stack is the nearest to the user:
             |     |         |    |
             |          |    |    |     ⇦ ☻
             |          |         |     user
z-index:  canvas  -1    0    1    2

   The stacking context background and most negative positioned stacking
   contexts are at the bottom of the stack, while the most positive
   positioned stacking contexts are at the top of the stack.

   The canvas is transparent if contained within another, and given a
   UA-defined color if it is not. It is infinite in extent and contains
   the root element. Initially, the viewport is anchored with its top left
   corner at the canvas origin.

   The painting order for the descendants of an element generating a
   stacking context (see the 'z-index' property) is:
    1. If the element is a root element:
         1. background color of element over the entire canvas.
         2. background image of element, over the entire canvas, anchored
            at the origin that would be used if it was painted for the
            root element.
    2. If the element is a block, list-item, or other block equivalent:
         1. background color of element unless it is the root element.
         2. background image of element unless it is the root element.
         3. border of element.
       Otherwise, if the element is a block level table:
         1. table backgrounds (color then image) unless it is the root
            element.
         2. column group backgrounds (color then image).
         3. column backgrounds (color then image).
         4. row group backgrounds (color then image).
         5. row backgrounds (color then image).
         6. cell backgrounds (color then image).
         7. all table borders (in tree order for separated borders).
    3. Stacking contexts formed by positioned descendants with negative
       z-indices (excluding 0) in z-index order (most negative first) then
       tree order.
    4. For all its in-flow, non-positioned, block-level descendants in
       tree order: If the element is a block, list-item, or other block
       equivalent:
         1. background color of element.
         2. background image of element.
         3. border of element.
       Otherwise, the element is a table:
         1. table backgrounds (color then image).
         2. column group backgrounds (color then image).
         3. column backgrounds (color then image).
         4. row group backgrounds (color then image).
         5. row backgrounds (color then image).
         6. cell backgrounds (color then image).
         7. all table borders (in tree order for separated borders).
    5. All non-positioned floating descendants, in tree order. For each
       one of these, treat the element as if it created a new stacking
       context, but any positioned descendants and descendants which
       actually create a new stacking context should be considered part of
       the parent stacking context, not this new one.
    6. If the element is an inline element that generates a stacking
       context, then:
         1. For each line box that the element is in:
              1. Jump to 7.2.1 for the box(es) of the element in that line
                 box (in tree order).
    7. Otherwise: first for the element, then for all its in-flow,
       non-positioned, block-level descendants in tree order:
         1. If the element is a block-level replaced element, then: the
            replaced content, atomically.
         2. Otherwise, for each line box of that element:
              1. For each box that is a child of that element, in that
                 line box, in tree order:
                   1. background color of element.
                   2. background image of element.
                   3. border of element.
                   4. For inline elements:
                        1. For all the element's in-flow, non-positioned,
                           inline-level children that are in this line
                           box, and all runs of text inside the element
                           that is on this line box, in tree order:
                             1. If this is a run of text, then:
                                  1. any underlining affecting the text of
                                     the element, in tree order of the
                                     elements applying the underlining
                                     (such that the deepest element's
                                     underlining, if any, is painted
                                     topmost and the root element's
                                     underlining, if any, is drawn
                                     bottommost).
                                  2. any overlining affecting the text of
                                     the element, in tree order of the
                                     elements applying the overlining
                                     (such that the deepest element's
                                     overlining, if any, is painted
                                     topmost and the root element's
                                     overlining, if any, is drawn
                                     bottommost).
                                  3. the text.
                                  4. any line-through affecting the text
                                     of the element, in tree order of the
                                     elements applying the line-through
                                     (such that the deepest element's
                                     line-through, if any, is painted
                                     topmost and the root element's
                                     line-through, if any, is drawn
                                     bottommost).
                             2. Otherwise, jump to 7.2.1 for that element.
                      For inline-block and inline-table elements:
                        1. For each one of these, treat the element as if
                           it created a new stacking context, but any
                           positioned descendants and descendants which
                           actually create a new stacking context should
                           be considered part of the parent stacking
                           context, not this new one.
                      For inline-level replaced elements:
                        1. the replaced content, atomically.
                 Some of the boxes may have been generated by line
                 splitting or the Unicode bidirectional algorithm.
              2. Optionally, the outline of the element (see 10 below).
         3. Optionally, if the element is block-level, the outline of the
            element (see 10 below).
    8. All positioned descendants with 'z-index: auto' or 'z-index: 0', in
       tree order. For those with 'z-index: auto', treat the element as if
       it created a new stacking context, but any positioned descendants
       and descendants which actually create a new stacking context should
       be considered part of the parent stacking context, not this new
       one. For those with 'z-index: 0', treat the stacking context
       generated atomically.
    9. Stacking contexts formed by positioned descendants with z-indices
       greater than or equal to 1 in z-index order (smallest first) then
       tree order.
   10. Finally, implementations that do not draw outlines in steps above
       must draw outlines from this stacking context at this stage. (It is
       recommended to draw outlines in this step and not in the steps
       above.)

E.3 Notes

   The background of the root element is only painted once, over the whole
   canvas.

   While the backgrounds of bidirectional inlines are painted in tree
   order, they are positioned in visual order. Since the positioning of
   inline backgrounds is unspecified in CSS 2.1, the exact result of these
   two requirements is UA-defined. CSS3 may define this in more detail.

                        Appendix F. Full property table

   This appendix is informative, not normative.

                    Name Values Initial value Applies to
                    (Default: all) Inherited? Percentages
                         (Default: N/A) Media groups
   'azimuth' <angle> | [[ left-side | far-left | left | center-left |
   center | center-right | right | far-right | right-side ] || behind ] |
   leftwards | rightwards | inherit center   yes   aural
   'background-attachment' scroll | fixed | inherit scroll   no   visual
   'background-color' <color> | transparent | inherit transparent   no
   visual
   'background-image' <uri> | none | inherit none   no   visual
   'background-position' [ [ <percentage> | <length> | left | center |
   right ] [ <percentage> | <length> | top | center | bottom ]? ] | [ [
   left | center | right ] || [ top | center | bottom ] ] | inherit 0% 0%
     no refer to the size of the box itself visual
   'background-repeat' repeat | repeat-x | repeat-y | no-repeat | inherit
   repeat   no   visual
   'background' ['background-color' || 'background-image' ||
   'background-repeat' || 'background-attachment' ||
   'background-position'] | inherit see individual properties   no allowed
   on 'background-position' visual
   'border-collapse' collapse | separate | inherit separate 'table' and
   'inline-table' elements yes   visual
   'border-color' [ <color> | transparent ]{1,4} | inherit see individual
   properties   no   visual
   'border-spacing' <length> <length>? | inherit 0 'table' and
   'inline-table' elements  yes   visual
   'border-style' <border-style>{1,4} | inherit see individual properties
     no   visual
   'border-top' 'border-right' 'border-bottom' 'border-left' [
   <border-width> || <border-style> || 'border-top-color' ] | inherit see
   individual properties   no   visual
   'border-top-color' 'border-right-color' 'border-bottom-color'
   'border-left-color' <color> | transparent | inherit the value of the
   'color' property   no   visual
   'border-top-style' 'border-right-style' 'border-bottom-style'
   'border-left-style' <border-style> | inherit none   no   visual
   'border-top-width' 'border-right-width' 'border-bottom-width'
   'border-left-width' <border-width> | inherit medium   no   visual
   'border-width' <border-width>{1,4} | inherit see individual properties
     no   visual
   'border' [ <border-width> || <border-style> || 'border-top-color' ] |
   inherit see individual properties   no   visual
   'bottom' <length> | <percentage> | auto | inherit auto positioned
   elements no refer to height of containing block visual
   'caption-side' top | bottom | inherit top 'table-caption' elements yes
     visual
   'clear' none | left | right | both | inherit none block-level elements
   no   visual
   'clip' <shape> | auto | inherit auto absolutely positioned elements no
     visual
   'color' <color> | inherit depends on user agent   yes   visual
   'content' normal | none | [ <string> | <uri> | <counter> |
   attr(<identifier>) | open-quote | close-quote | no-open-quote |
   no-close-quote ]+ | inherit normal :before and :after pseudo-elements
   no   all
   'counter-increment' [ <identifier> <integer>? ]+ | none | inherit none
     no   all
   'counter-reset' [ <identifier> <integer>? ]+ | none | inherit none   no
     all
   'cue-after' <uri> | none | inherit none   no   aural
   'cue-before' <uri> | none | inherit none   no   aural
   'cue' [ 'cue-before' || 'cue-after' ] | inherit see individual
   properties   no   aural
   'cursor' [ [<uri> ,]* [ auto | crosshair | default | pointer | move |
   e-resize | ne-resize | nw-resize | n-resize | se-resize | sw-resize |
   s-resize | w-resize | text | wait | help | progress ] ] | inherit auto
     yes   visual, interactive
   'direction' ltr | rtl | inherit ltr all elements, but see prose yes
   visual
   'display' inline | block | list-item | inline-block | table |
   inline-table | table-row-group | table-header-group |
   table-footer-group | table-row | table-column-group | table-column |
   table-cell | table-caption | none | inherit inline   no   all
   'elevation' <angle> | below | level | above | higher | lower | inherit
   level   yes   aural
   'empty-cells' show | hide | inherit show 'table-cell' elements yes
   visual
   'float' left | right | none | inherit none all, but see 9.7 no   visual
   'font-family' [[ <family-name> | <generic-family> ] [, <family-name>|
   <generic-family>]* ] | inherit depends on user agent   yes   visual
   'font-size' <absolute-size> | <relative-size> | <length> | <percentage>
   | inherit medium   yes refer to inherited font size visual
   'font-style' normal | italic | oblique | inherit normal   yes   visual
   'font-variant' normal | small-caps | inherit normal   yes   visual
   'font-weight' normal | bold | bolder | lighter | 100 | 200 | 300 | 400
   | 500 | 600 | 700 | 800 | 900 | inherit normal   yes   visual
   'font' [ [ 'font-style' || 'font-variant' || 'font-weight' ]?
   'font-size' [ / 'line-height' ]? 'font-family' ] | caption | icon |
   menu | message-box | small-caption | status-bar | inherit see
   individual properties   yes see individual properties visual
   'height' <length> | <percentage> | auto | inherit auto all elements but
   non-replaced inline elements, table columns, and column groups no see
   prose visual
   'left' <length> | <percentage> | auto | inherit auto positioned
   elements no refer to width of containing block visual
   'letter-spacing' normal | <length> | inherit normal   yes   visual
   'line-height' normal | <number> | <length> | <percentage> | inherit
   normal   yes refer to the font size of the element itself visual
   'list-style-image' <uri> | none | inherit none elements with 'display:
   list-item' yes   visual
   'list-style-position' inside | outside | inherit outside elements with
   'display: list-item' yes   visual
   'list-style-type' disc | circle | square | decimal |
   decimal-leading-zero | lower-roman | upper-roman | lower-greek |
   lower-latin | upper-latin | armenian | georgian | lower-alpha |
   upper-alpha | none | inherit disc elements with 'display: list-item'
   yes   visual
   'list-style' [ 'list-style-type' || 'list-style-position' ||
   'list-style-image' ] | inherit see individual properties elements with
   'display: list-item' yes   visual
   'margin-right' 'margin-left' <margin-width> | inherit 0 all elements
   except elements with table display types other than table-caption,
   table and inline-table no refer to width of containing block visual
   'margin-top' 'margin-bottom' <margin-width> | inherit 0 all elements
   except elements with table display types other than table-caption,
   table and inline-table no refer to width of containing block visual
   'margin' <margin-width>{1,4} | inherit see individual properties all
   elements except elements with table display types other than
   table-caption, table and inline-table no refer to width of containing
   block visual
   'max-height' <length> | <percentage> | none | inherit none all elements
   but non-replaced inline elements, table columns, and column groups no
   see prose visual
   'max-width' <length> | <percentage> | none | inherit none all elements
   but non-replaced inline elements, table rows, and row groups no refer
   to width of containing block visual
   'min-height' <length> | <percentage> | inherit 0 all elements but
   non-replaced inline elements, table columns, and column groups no see
   prose visual
   'min-width' <length> | <percentage> | inherit 0 all elements but
   non-replaced inline elements, table rows, and row groups no refer to
   width of containing block visual
   'orphans' <integer> | inherit 2 block container elements yes   visual,
   paged
   'outline-color' <color> | invert | inherit invert   no   visual,
   interactive
   'outline-style' <border-style> | inherit none   no   visual,
   interactive
   'outline-width' <border-width> | inherit medium   no   visual,
   interactive
   'outline' [ 'outline-color' || 'outline-style' || 'outline-width' ] |
   inherit see individual properties   no   visual, interactive
   'overflow' visible | hidden | scroll | auto | inherit visible block
   containers no   visual
   'padding-top' 'padding-right' 'padding-bottom' 'padding-left'
   <padding-width> | inherit 0 all elements except table-row-group,
   table-header-group, table-footer-group, table-row, table-column-group
   and table-column no refer to width of containing block visual
   'padding' <padding-width>{1,4} | inherit see individual properties all
   elements except table-row-group, table-header-group,
   table-footer-group, table-row, table-column-group and table-column no
   refer to width of containing block visual
   'page-break-after' auto | always | avoid | left | right | inherit auto
   block-level elements (but see text) no   visual, paged
   'page-break-before' auto | always | avoid | left | right | inherit auto
   block-level elements (but see text) no   visual, paged
   'page-break-inside' avoid | auto | inherit auto block-level elements
   (but see text) no   visual, paged
   'pause-after' <time> | <percentage> | inherit 0   no see prose aural
   'pause-before' <time> | <percentage> | inherit 0   no see prose aural
   'pause' [ [<time> | <percentage>]{1,2} ] | inherit see individual
   properties   no see descriptions of 'pause-before' and 'pause-after'
   aural
   'pitch-range' <number> | inherit 50   yes   aural
   'pitch' <frequency> | x-low | low | medium | high | x-high | inherit
   medium   yes   aural
   'play-during' <uri> [ mix || repeat ]? | auto | none | inherit auto
   no   aural
   'position' static | relative | absolute | fixed | inherit static   no
   visual
   'quotes' [<string> <string>]+ | none | inherit depends on user agent
   yes   visual
   'richness' <number> | inherit 50   yes   aural
   'right' <length> | <percentage> | auto | inherit auto positioned
   elements no refer to width of containing block visual
   'speak-header' once | always | inherit once elements that have table
   header information yes   aural
   'speak-numeral' digits | continuous | inherit continuous   yes   aural
   'speak-punctuation' code | none | inherit none   yes   aural
   'speak' normal | none | spell-out | inherit normal   yes   aural
   'speech-rate' <number> | x-slow | slow | medium | fast | x-fast |
   faster | slower | inherit medium   yes   aural
   'stress' <number> | inherit 50   yes   aural
   'table-layout' auto | fixed | inherit auto 'table' and 'inline-table'
   elements no   visual
   'text-align' left | right | center | justify | inherit a nameless value
   that acts as 'left' if 'direction' is 'ltr', 'right' if 'direction' is
   'rtl' block containers yes   visual
   'text-decoration' none | [ underline || overline || line-through ||
   blink ] | inherit none   no (see prose)   visual
   'text-indent' <length> | <percentage> | inherit 0 block containers yes
   refer to width of containing block visual
   'text-transform' capitalize | uppercase | lowercase | none | inherit
   none   yes   visual
   'top' <length> | <percentage> | auto | inherit auto positioned elements
   no refer to height of containing block visual
   'unicode-bidi' normal | embed | bidi-override | inherit normal all
   elements, but see prose no   visual
   'vertical-align' baseline | sub | super | top | text-top | middle |
   bottom | text-bottom | <percentage> | <length> | inherit baseline
   inline-level and 'table-cell' elements no refer to the 'line-height' of
   the element itself visual
   'visibility' visible | hidden | collapse | inherit visible   yes
   visual
   'voice-family' [[<specific-voice> | <generic-voice> ],]*
   [<specific-voice> | <generic-voice> ] | inherit depends on user agent
   yes   aural
   'volume' <number> | <percentage> | silent | x-soft | soft | medium |
   loud | x-loud | inherit medium   yes refer to inherited value aural
   'white-space' normal | pre | nowrap | pre-wrap | pre-line | inherit
   normal   yes   visual
   'widows' <integer> | inherit 2 block container elements yes   visual,
   paged
   'width' <length> | <percentage> | auto | inherit auto all elements but
   non-replaced inline elements, table rows, and row groups no refer to
   width of containing block visual
   'word-spacing' normal | <length> | inherit normal   yes   visual
   'z-index' auto | <integer> | inherit auto positioned elements no
   visual

                         Appendix G. Grammar of CSS 2.1

   Contents
     * G.1 Grammar
     * G.2 Lexical scanner
     * G.3 Comparison of tokenization in CSS 2.1 and CSS1
     * G.4 Implementation note

   This appendix is non-normative.

   The grammar below defines the syntax of CSS 2.1. It is in some sense,
   however, a superset of CSS 2.1 as this specification imposes additional
   semantic constraints not expressed in this grammar. A conforming UA
   must also adhere to the forward-compatible parsing rules, the selectors
   notation, the property and value notation, and the unit notation.
   However, not all syntactically correct CSS can take effect, since the
   document language may impose restrictions that are not in CSS, e.g.,
   HTML imposes restrictions on the possible values of the "class"
   attribute.

G.1 Grammar

   The grammar below is LALR(1) (but note that most UA's should not use it
   directly, since it does not express the parsing conventions, only the
   CSS 2.1 syntax). The format of the productions is optimized for human
   consumption and some shorthand notation beyond Yacc (see [YACC]) is
   used:
     * *: 0 or more
     * +: 1 or more
     * ?: 0 or 1
     * |: separates alternatives
     * [ ]: grouping

   The productions are:
stylesheet
  : [ CHARSET_SYM STRING ';' ]?
    [S|CDO|CDC]* [ import [ CDO S* | CDC S* ]* ]*
    [ [ ruleset | media | page ] [ CDO S* | CDC S* ]* ]*
  ;
import
  : IMPORT_SYM S*
    [STRING|URI] S* media_list? ';' S*
  ;
media
  : MEDIA_SYM S* media_list '{' S* ruleset* '}' S*
  ;
media_list
  : medium [ COMMA S* medium]*
  ;
medium
  : IDENT S*
  ;
page
  : PAGE_SYM S* pseudo_page?
    '{' S* declaration? [ ';' S* declaration? ]* '}' S*
  ;
pseudo_page
  : ':' IDENT S*
  ;
operator
  : '/' S* | ',' S*
  ;
combinator
  : '+' S*
  | '>' S*
  ;
unary_operator
  : '-' | '+'
  ;
property
  : IDENT S*
  ;
ruleset
  : selector [ ',' S* selector ]*
    '{' S* declaration? [ ';' S* declaration? ]* '}' S*
  ;
selector
  : simple_selector [ combinator selector | S+ [ combinator? selector ]? ]?
  ;
simple_selector
  : element_name [ HASH | class | attrib | pseudo ]*
  | [ HASH | class | attrib | pseudo ]+
  ;
class
  : '.' IDENT
  ;
element_name
  : IDENT | '*'
  ;
attrib
  : '[' S* IDENT S* [ [ '=' | INCLUDES | DASHMATCH ] S*
    [ IDENT | STRING ] S* ]? ']'
  ;
pseudo
  : ':' [ IDENT | FUNCTION S* [IDENT S*]? ')' ]
  ;
declaration
  : property ':' S* expr prio?
  ;
prio
  : IMPORTANT_SYM S*
  ;
expr
  : term [ operator? term ]*
  ;
term
  : unary_operator?
    [ NUMBER S* | PERCENTAGE S* | LENGTH S* | EMS S* | EXS S* | ANGLE S* |
      TIME S* | FREQ S* ]
  | STRING S* | IDENT S* | URI S* | hexcolor | function
  ;
function
  : FUNCTION S* expr ')' S*
  ;
/*
 * There is a constraint on the color that it must
 * have either 3 or 6 hex-digits (i.e., [0-9a-fA-F])
 * after the "#"; e.g., "#000" is OK, but "#abcd" is not.
 */
hexcolor
  : HASH S*
  ;

G.2 Lexical scanner

   The following is the tokenizer, written in Flex (see [FLEX]) notation.
   The tokenizer is case-insensitive.

   The "\377" represents the highest character number that current
   versions of Flex can deal with (decimal 255). It should be read as
   "\4177777" (decimal 1114111), which is the highest possible code point
   in Unicode/ISO-10646.
%option case-insensitive

h               [0-9a-f]
nonascii        [\240-\377]
unicode         \\{h}{1,6}(\r\n|[ \t\r\n\f])?
escape          {unicode}|\\[^\r\n\f0-9a-f]
nmstart         [_a-z]|{nonascii}|{escape}
nmchar          [_a-z0-9-]|{nonascii}|{escape}
string1         \"([^\n\r\f\\"]|\\{nl}|{escape})*\"
string2         \'([^\n\r\f\\']|\\{nl}|{escape})*\'
badstring1      \"([^\n\r\f\\"]|\\{nl}|{escape})*\\?
badstring2      \'([^\n\r\f\\']|\\{nl}|{escape})*\\?
badcomment1     \/\*[^*]*\*+([^/*][^*]*\*+)*
badcomment2     \/\*[^*]*(\*+[^/*][^*]*)*
baduri1         url\({w}([!#$%&*-\[\]-~]|{nonascii}|{escape})*{w}
baduri2         url\({w}{string}{w}
baduri3         url\({w}{badstring}
comment         \/\*[^*]*\*+([^/*][^*]*\*+)*\/
ident           -?{nmstart}{nmchar}*
name            {nmchar}+
num             [0-9]+|[0-9]*"."[0-9]+
string          {string1}|{string2}
badstring       {badstring1}|{badstring2}
badcomment      {badcomment1}|{badcomment2}
baduri          {baduri1}|{baduri2}|{baduri3}
url             ([!#$%&*-~]|{nonascii}|{escape})*
s               [ \t\r\n\f]+
w               {s}?
nl              \n|\r\n|\r|\f

A               a|\\0{0,4}(41|61)(\r\n|[ \t\r\n\f])?
C               c|\\0{0,4}(43|63)(\r\n|[ \t\r\n\f])?
D               d|\\0{0,4}(44|64)(\r\n|[ \t\r\n\f])?
E               e|\\0{0,4}(45|65)(\r\n|[ \t\r\n\f])?
G               g|\\0{0,4}(47|67)(\r\n|[ \t\r\n\f])?|\\g
H               h|\\0{0,4}(48|68)(\r\n|[ \t\r\n\f])?|\\h
I               i|\\0{0,4}(49|69)(\r\n|[ \t\r\n\f])?|\\i
K               k|\\0{0,4}(4b|6b)(\r\n|[ \t\r\n\f])?|\\k
L               l|\\0{0,4}(4c|6c)(\r\n|[ \t\r\n\f])?|\\l
M               m|\\0{0,4}(4d|6d)(\r\n|[ \t\r\n\f])?|\\m
N               n|\\0{0,4}(4e|6e)(\r\n|[ \t\r\n\f])?|\\n
O               o|\\0{0,4}(4f|6f)(\r\n|[ \t\r\n\f])?|\\o
P               p|\\0{0,4}(50|70)(\r\n|[ \t\r\n\f])?|\\p
R               r|\\0{0,4}(52|72)(\r\n|[ \t\r\n\f])?|\\r
S               s|\\0{0,4}(53|73)(\r\n|[ \t\r\n\f])?|\\s
T               t|\\0{0,4}(54|74)(\r\n|[ \t\r\n\f])?|\\t
U               u|\\0{0,4}(55|75)(\r\n|[ \t\r\n\f])?|\\u
X               x|\\0{0,4}(58|78)(\r\n|[ \t\r\n\f])?|\\x
Z               z|\\0{0,4}(5a|7a)(\r\n|[ \t\r\n\f])?|\\z

%%

{s}                     {return S;}

\/\*[^*]*\*+([^/*][^*]*\*+)*\/          /* ignore comments */
{badcomment}                         /* unclosed comment at EOF */

"<!--"          {return CDO;}
"-->"                   {return CDC;}
"~="                    {return INCLUDES;}
"|="                    {return DASHMATCH;}

{string}                {return STRING;}
{badstring}             {return BAD_STRING;}

{ident}                 {return IDENT;}

"#"{name}               {return HASH;}

@{I}{M}{P}{O}{R}{T}     {return IMPORT_SYM;}
@{P}{A}{G}{E}           {return PAGE_SYM;}
@{M}{E}{D}{I}{A}        {return MEDIA_SYM;}
"@charset "             {return CHARSET_SYM;}

"!"({w}|{comment})*{I}{M}{P}{O}{R}{T}{A}{N}{T}  {return IMPORTANT_SYM;}

{num}{E}{M}             {return EMS;}
{num}{E}{X}             {return EXS;}
{num}{P}{X}             {return LENGTH;}
{num}{C}{M}             {return LENGTH;}
{num}{M}{M}             {return LENGTH;}
{num}{I}{N}             {return LENGTH;}
{num}{P}{T}             {return LENGTH;}
{num}{P}{C}             {return LENGTH;}
{num}{D}{E}{G}          {return ANGLE;}
{num}{R}{A}{D}          {return ANGLE;}
{num}{G}{R}{A}{D}       {return ANGLE;}
{num}{M}{S}             {return TIME;}
{num}{S}                {return TIME;}
{num}{H}{Z}             {return FREQ;}
{num}{K}{H}{Z}          {return FREQ;}
{num}{ident}            {return DIMENSION;}

{num}%                  {return PERCENTAGE;}
{num}                   {return NUMBER;}

"url("{w}{string}{w}")" {return URI;}
"url("{w}{url}{w}")"    {return URI;}
{baduri}                {return BAD_URI;}

{ident}"("              {return FUNCTION;}

.                       {return *yytext;}

G.3 Comparison of tokenization in CSS 2.1 and CSS1

   There are some differences in the syntax specified in the CSS1
   recommendation ([CSS1]), and the one above. Most of these are due to
   new tokens in CSS2 that did not exist in CSS1. Others are because the
   grammar has been rewritten to be more readable. However, there are some
   incompatible changes, that were felt to be errors in the CSS1 syntax.
   They are explained below.
     * CSS1 style sheets could only be in 1-byte-per-character encodings,
       such as ASCII and ISO-8859-1. CSS 2.1 has no such limitation. In
       practice, there was little difficulty in extrapolating the CSS1
       tokenizer, and some UAs have accepted 2-byte encodings.
     * CSS1 only allowed four hex-digits after the backslash (\) to refer
       to Unicode characters, CSS2 allows six. Furthermore, CSS2 allows a
       white space character to delimit the escape sequence. E.g.,
       according to CSS1, the string "\abcdef" has 3 letters (\abcd, e,
       and f), according to CSS2 it has only one (\abcdef).
     * The tab character (ASCII 9) was not allowed in strings. However,
       since strings in CSS1 were only used for font names and for URLs,
       the only way this can lead to incompatibility between CSS1 and CSS2
       is if a style sheet contains a font family that has a tab in its
       name.
     * Similarly, newlines (escaped with a backslash) were not allowed in
       strings in CSS1.
     * CSS2 parses a number immediately followed by an identifier as a
       DIMENSION token (i.e., an unknown unit), CSS1 parsed it as a number
       and an identifier. That means that in CSS1, the declaration 'font:
       10pt/1.2serif' was correct, as was 'font: 10pt/12pt serif'; in
       CSS2, a space is required before "serif". (Some UAs accepted the
       first example, but not the second.)
     * In CSS1, a class name could start with a digit (".55ft"), unless it
       was a dimension (".55in"). In CSS2, such classes are parsed as
       unknown dimensions (to allow for future additions of new units). To
       make ".55ft" a valid class, CSS2 requires the first digit to be
       escaped (".\35 5ft")

G.4 Implementation note

   The lexical scanner for the CSS core syntax in section 4.1.1 can be
   implemented as a scanner without back-up. In Lex notation, that
   requires the addition of the following patterns (which do not change
   the returned tokens, only the efficiency of the scanner):
{ident}/\\          return IDENT;
#{name}/\\          return HASH;
@{ident}/\\         return ATKEYWORD;
#/\\                return DELIM;
@/\\                return DELIM;
@/-                 return DELIM;
@/-\\               return DELIM;
-/\\                return DELIM;
-/-                 return DELIM;
\</!                return DELIM;
\</!-               return DELIM;
{num}{ident}/\\     return DIMENSION;
{num}/\\            return NUMBER;
{num}/-             return NUMBER;
{num}/-\\           return NUMBER;
[0-9]+/\.           return NUMBER;
u/\+                return IDENT;
u\+[0-9a-f?]{1,6}/- return UNICODE_RANGE;

        Appendix H: Has been intentionally left blank

                               Appendix I. Index

   This appendix is informative, not normative.

   A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

     * :active, 2
     * :after, 1, 2
     * :before, 1, 2
     * :first, 1
     * :first-child, 1
     * :first-letter, 1
     * :first-line, 1
     * :focus, 1
     * :hover, 1
     * :lang, 1
     * :left, 1
     * :link, 1
     * :right, 1
     * :visited, 1
     * =, 1
     * ~=, 1
     * |=, 1


     * @charset, 1, 2, 3
     * "@charset", 1
     * @import, 1, 2, 3
     * @media, 1, 2
     * @page, 1


     * absolute length, 1
     * absolutely positioned element, 1
     * active (pseudo-class), 1
     * actual value, 1
     * adjoining margins, 1
     * after, 1
     * 'all' media group, 1
     * ancestor, 1
     * <angle>, 1, 2
          + definition of, 1
     * anonymous, 1
     * anonymous boxes., 1
     * anonymous inline boxes, 1
     * armenian, 1
     * at-rule, 1
     * at-rules, 1
     * atomic inline-level box, 1
     * attr(), 1
     * attribute, 1
     * 'audio' media group, 1
     * auditory icon, 1
     * Author, 1
     * authoring tool, 1
     * automatic numbering, 1
     * 'azimuth', 1


     * 'background', 1
     * 'background-attachment', 1
     * 'background-color', 1
     * 'background-image', 1
     * 'background-position', 1
     * 'background-repeat', 1
     * backslash escapes, 1
     * before, 1
     * bidirectionality (bidi), 1
     * 'bitmap' media group, 1
     * block, 1
     * block box, 1
     * block container box, 1
     * 'block', definition of, 1
     * block-level box, 1
     * block-level element, 1
     * BOM, 1
     * border box, 1
     * border edge, 1
     * 'border', 1
     * 'border-bottom', 1
     * 'border-bottom-color', 1
     * 'border-bottom-style', 1
     * 'border-bottom-width', 1
     * 'border-collapse', 1
     * 'border-color', 1
     * 'border-left', 1
     * 'border-left-color', 1
     * 'border-left-style', 1
     * 'border-left-width', 1
     * 'border-right', 1
     * 'border-right-color', 1
     * 'border-right-style', 1
     * 'border-right-width', 1
     * 'border-spacing', 1
     * <border-style>, 1
     * <border-style>, definition of, 1
     * 'border-style', 1
     * 'border-top', 1
     * 'border-top-color', 1
     * 'border-top-style', 1
     * 'border-top-width', 1
     * <border-width>
          + definition of, 1
     * 'border-width', 1
     * border
          + of a box, 1
     * <bottom>
          + definition of, 1
     * 'bottom', 1
     * box
          + border, 1
          + content, 1
          + content height, 1
          + content width, 1
          + margin, 1
          + overflow, 1
          + padding, 1


     * canvas, 1, 2
     * 'caption-side', 1
     * cascade, 1
     * case sensitivity, 1
     * character encoding, 1
          + default, 1
          + user agent's determination of, 1
     * child, 1
     * child selector, 1
     * circle, 1
     * 'clear', 1
     * clearance, 1
     * 'clip', 1
     * clipping region, 1
     * close-quote, 1, 2
     * collapse, 1
     * collapse through, 1
     * collapsing margin, 1
     * color, 1
     * <color>, 1, 2
          + definition of, 1
     * 'color', 1
     * combinator, 1
     * comments, 1
     * computed value, 1
     * conditional import, 1
     * conformance, 1, 2
     * consecutive, 1
     * containing block, 1, 2, 3
          + initial, 1
     * content, 1
     * content box, 1
     * content edge, 1
     * 'content', 1
     * content
          + of a box, 1
          + rendered, 1
     * 'continuous' media group, 1
     * <counter>, 1
     * <counter>, definition of, 1
     * counter(), 1
     * 'counter-increment', 1
     * 'counter-reset', 1
     * counters, 1
     * 'cue', 1
     * 'cue-after', 1
     * 'cue-before', 1
     * cursive, definition of, 1
     * 'cursor', 1


     * 'dashed', 1, 2
     * decimal, 1
     * decimal-leading-zero, 1
     * declaration, 1
     * declaration block, 1
     * default style sheet, 1
     * default
          + character encoding, 1
     * descendant, 1
     * descendant-selectors, 1
     * 'direction', 1
     * disc, 1
     * 'display', 1
     * document language, 1
     * document tree, 1
     * 'dotted', 1, 2
     * 'double', 1, 2
     * drop caps, 1
     * DTD, 1, 2


     * element, 1
          + following, 1
          + preceding, 1
     * 'elevation', 1
     * em (unit), 1
     * empty, 1
     * 'empty-cells', 1
     * ex (unit), 1
     * exact matching, 1


     * fantasy, definition of, 1
     * fictional tag sequence, 1, 2, 3
     * first-child, 1
     * first-letter, 1
     * first-line, 1
     * float rules, 1
     * 'float', 1
     * flow of an element, 1
     * focus, 1
     * focus (pseudo-class), 1
     * following element, 1
     * 'font', 1
     * 'font-family', 1
     * 'font-size', 1
     * 'font-style', 1
     * 'font-variant', 1
     * 'font-weight', 1
     * formatting context, 1
     * formatting structure, 1
     * forward-compatible parsing, 1
     * <frequency>, 1
          + definition of, 1


     * generated content, 1
     * <generic-voice>, definition of, 1
     * georgian, 1
     * 'grid' media group, 1
     * 'groove', 1, 2


     * 'height', 1
     * 'hidden, 1
     * 'hidden', 1
     * hover (pseudo-class), 1
     * hyphen-separated matching, 1


     * identifier, 1
     * identifier, definition of, 1
     * ignore, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17
     * in-flow, 1
     * inherit, definition of, 1
     * initial caps, 1
     * initial containing block, 1
     * initial value, 1
     * inline box, 1
     * 'inline', definition of, 1
     * 'inline-block', definition of, 1
     * inline-level box, 1
     * inline-level element, 1
     * inline-table, 1
     * inner edge, 1
     * 'inset', 1, 2
     * <integer>, 1
          + definition of, 1
     * 'interactive media group, 1
     * internal table box, 1
     * internal table element, 1
     * intrinsic dimensions, 1
     * invert, 1
     * iso-10646, 1


     * LALR(1), 1
     * lang (pseudo-class), 1
     * language (human), 1
     * language code, 1
     * <left>
          + definition of, 1
     * 'left', 1
     * <length>, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
          + definition of, 1
     * 'letter-spacing', 1
     * ligatures, 1
     * line box, 1
     * line-box, 1
     * 'line-height', 1
     * link (pseudo-class), 1
     * list properties, 1
     * 'list-item', definition of, 1
     * 'list-style', 1
     * 'list-style-image', 1
     * 'list-style-position', 1
     * 'list-style-type', 1
     * lower-greek, 1
     * lower-latin, 1
     * lower-roman, 1


     * mapping elements to table parts, 1
     * margin box, 1
     * margin edge, 1
     * 'margin', 1
     * 'margin-bottom', 1
     * 'margin-left', 1
     * 'margin-right', 1
     * 'margin-top', 1
     * <margin-width>
          + definition of, 1
     * margin
          + of a box, 1
     * match, 1
     * 'max-height', 1
     * 'max-width', 1
     * MAY, 1
     * media, 1
     * media group, 1
     * media-dependent import, 1
     * message entity, 1
     * 'min-height', 1
     * 'min-width', 1
     * monospace, definition of, 1
     * multiple declarations, 1
     * MUST, 1
     * MUST NOT, 1


     * newline, 1
     * no-close-quote, 1, 2
     * no-open-quote, 1, 2
     * none, 1
     * 'none'
          + as border style, 1, 2
          + as display value, 1
     * normal, 1
     * <number>, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
          + definition of, 1


     * open-quote, 1, 2
     * OPTIONAL, 1
     * 'orphans', 1
     * out of flow, 1
     * outer edge, 1
     * outline, 1
     * 'outline', 1
     * 'outline-color', 1
     * 'outline-style', 1
     * 'outline-width', 1
     * 'outset', 1, 2
     * overflow, 1
     * 'overflow', 1


     * padding box, 1
     * padding edge, 1
     * 'padding', 1
     * 'padding-bottom', 1
     * 'padding-left', 1
     * 'padding-right', 1
     * 'padding-top', 1
     * <padding-width>
          + definition of, 1
     * padding
          + of a box, 1
     * page area, 1
     * page box, 1
     * page selector, 1
     * 'page-break-after', 1
     * 'page-break-before', 1
     * 'page-break-inside', 1
     * page-context, 1
     * 'paged' media group, 1
     * parent, 1
     * 'pause', 1
     * 'pause-after', 1
     * 'pause-before', 1
     * <percentage>, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10
          + definition of, 1
     * 'pitch', 1
     * 'pitch-range', 1
     * pixel, 1
     * 'play-during', 1
     * 'position', 1
     * positioned element/box, 1
     * positioning scheme, 1
     * preceding element, 1
     * principal block-level box, 1
     * proper table child, 1
     * proper table row parent, 1
     * Property, 1
     * property, 1
     * 'property-name', 1
     * pseudo-class
          + :first, 1
          + :left, 1
          + :right, 1
     * pseudo-classes, 1
          + :active, 1
          + :focus, 1
          + :hover, 1
          + :lang, 1
          + :link, 1
          + :visited, 1
     * pseudo-elements, 1
          + :after, 1, 2
          + :before, 1, 2
          + :first-letter, 1
          + :first-line, 1, 2


     * quad width, 1
     * 'quotes', 1


     * RECOMMENDED, 1
     * reference pixel, 1
     * relative positioning, 1
     * relative units, 1
     * rendered content, 1
     * replaced element, 1
     * REQUIRED, 1
     * 'richness', 1
     * 'ridge', 1, 2
     * <right>
          + definition of, 1
     * 'right', 1
     * root, 1
     * row group box, 1
     * row groups, 1
     * rule sets, 1
     * run-in, 1


     * sans-serif, definition of, 1
     * scope, 1
     * screen reader, 1
     * selector, 1, 2, 3, 4
          + match, 1
          + subject of, 1
     * separated borders, 1
     * serif, definition of, 1
     * SHALL, 1
     * SHALL NOT, 1
     * <shape>
          + definition of, 1
     * sheet, 1
     * shorthand property, 1, 2, 3
     * SHOULD, 1
     * SHOULD NOT, 1
     * sibling, 1
     * simple selector, 1
     * 'solid', 1, 2
     * source document, 1
     * space-separated matching, 1
     * 'speak', 1
     * 'speak-header', 1
     * 'speak-numeral', 1
     * 'speak-punctuation', 1
     * <specific-voice>
          + definition of, 1
     * specified value, 1
     * 'speech' media group, 1
     * 'speech-rate', 1
     * square, 1
     * stack level, 1
     * stacking context, 1
     * statements, 1
     * 'static' media group, 1
     * 'stress', 1
     * string, 1
     * <string>, 1, 2, 3
     * <string>, definition of, 1
     * illegal, 1
     * style sheet, 1
     * subject (of selector), 1
     * system fonts, 1


     * table, 1
     * table element, 1
          + internal, 1
     * table-caption, 1
     * table-cell, 1
     * table-column, 1
     * table-column-group, 1
     * table-footer-group, 1
     * table-header-group, 1
     * 'table-layout', 1
     * table-row, 1
     * table-row-group, 1
     * tables, 1
     * tabular container, 1
     * 'tactile' media group, 1
     * 'text-align', 1
     * 'text-decoration', 1
     * 'text-indent', 1
     * 'text-transform', 1
     * text/css, 1
     * <time>, 1
          + definition of, 1
     * tokenizer, 1
     * <top>
          + definition of, 1
     * 'top', 1
     * type selector, 1


     * UA, 1
     * unicode, 1
     * 'unicode-bidi', 1
     * universal selector, 1
     * upper-latin, 1
     * upper-roman, 1
     * <uri>, 1, 2, 3, 4, 5, 6, 7
          + definition of, 1
     * used value, 1
     * User, 1
     * user agent, 1
     * User agent (UA), 1
     * UTF-8, 1


     * valid style sheet, 1
     * validity, 1
     * value, 1
     * 'vertical-align', 1
     * viewport, 1
     * 'visibility', 1
     * visited (pseudo-class), 1
     * visual formatting model, 1
     * 'visual' media group, 1
     * 'voice-family', 1
     * volume, 1
     * 'volume', 1


     * 'white-space', 1
     * 'widows', 1
     * 'width', 1
     * 'word-spacing', 1


     * x-height, 1


     * 'z-index', 1