Developer Newsletter

Appendix C. Changes

Contents

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.

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 Whitespace: 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 Acknowledgements

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 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 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.

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 4.3.6 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.2.18 Section 4.3.8 Unsupported Values

Added this section to recommend that unsupported properties and values be ignored as if they were invalid.

C.2.19 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 nay @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.2.20 Section 5.8.1 Matching attributes and attribute values

RFC 3066 replaces RFC 1766.

C.2.21 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.2.22 Section 5.9 ID selectors

Specified how to match elements with two or more ID attributes.

C.2.23 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.2.24 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.2.25 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.2.26 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.2.27 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.2.28 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.2.29 Section 6.4.1 Cascading order

Changed suggestion that user be able to turn off author styles to a requirement.

C.2.30 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.2.31 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.2.32 Section 7.3 Recognized Media Types

Added 'speech' media type.

Marked "Media" field in property descriptions informative.

C.2.33 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.2.34 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.2.35 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.

C.2.36 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.2.37 Section 8.5.2 Border color

'transparent' can now be specified independently for each border side, on par with <color>.

C.2.38 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.2.39 Section 8.6 The box model for inline elements in bidirection context

Added this new section to specify layout of inline boxes when affected by bidi.

C.2.40 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.2.41 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.2.42 Section 9.2.2.1 Anonymous inline boxes

Specified that collapsed whitespace does not generate anonymous inline boxes.

C.2.43 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.2.44 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.2.45 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 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.2.46 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.2.47 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.2.48 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.2.49 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.2.50 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.2.51 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.2.52 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.2.53 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.2.54 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.2.55 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 doesn't 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.2.56 Chapter 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.2.57 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.2.58 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.2.59 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.2.60 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.

C.2.61 Section 10.3.3 Block-level, non-replaced elements in normal flow

Added the vertical scrollbar width to the horizontal constraint equation.

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.2.62 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.2.63 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.2.64 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.2.65 Section 10.3.7 Absolutely positioned, non-replaced elements

Defined the static position of an element more precisely.

Added vertical scrollbar width to the horizontal restraint equation.

Rewrote constraint rules.

C.2.66 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.

In rule 4 (formerly rule 5), prevented 'auto' left and right margins in resulting in a negative margin on the start edge.

C.2.67 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 aribtrary 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.2.68 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.2.69 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 accomodate any normal-flow descendant floats.)

C.2.70 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.2.71 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

Specified that for inline elements, the margin box is used when calculating the height of the line box.

C.2.72 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.2.73 Section 10.6.4 Absolutely positioned, non-replaced elements

Defined the static position of an element more precisely.

Added vertical scrollbar width to the horizontal restraint equation.

Rewrote constraint rules.

C.2.74 Section 10.6.5 Absolutely positioned, replaced elements

In rule 1, applied sizing rules from section 10.6.2.

C.2.75 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.

C.2.76 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.2.77 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.2.78 Section 11.1 Overflow and clipping

Specified that 'overflow' clips to the padding edge.

C.2.79 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.

C.2.80 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 indiciates 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.2.81 Section 11.2 Visibility

The 'visibility' property is now defined to inherit, and descendant elements can override an ancestor's hidden visibility.

C.2.82 Chapter 12 Generated content, automatic numbering, and lists

Moved all discussion of aural rendering to Appendix A.

C.2.83 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.2.84 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.2.85 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.2.86 Section 12.4 Automatic counters and numbering

Defined what a rule with duplicate counters, such as 'counter-reset: section 2 section', means.

C.2.87 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.2.88 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.2.89 Section 12.5.1 Lists

The list styles 'hebrew', 'armenian', 'georgian', 'cjk-ideographs', '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.

C.2.90 Chapter 13 Paged media

The 'size', 'marks', and 'page' properties are not part of CSS 2.1.

C.2.91 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.2.92 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.

C.2.93 Section 13.3.3 Allowed page breaks

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.2.94 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.

C.2.95 Section 14.3 Gamma correction

The contents of this section is now a non-normative note.

C.2.96 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.2.97 Section 15.2 Font matching algorithm

In this section (previously 15.5), in step 5 (prevously 8) of the font matching algorith, 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.2.98 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.2.99 Section 15.5 Small-caps

The 'font-variant' property's effect is no longer restricted to bicameral scripts.

C.2.100 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.2.101 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.2.102 Chapter 16 Text

The 'text-shadow' property is not in CSS 2.1.

C.2.103 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.2.104 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 ony 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.2.105 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.2.106 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.2.107 Section 16.6 Whitespace

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.2.108 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.2.109 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.2.110 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.2.111 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.2.112 Section 17.4.1 Caption position and alignment

The 'left' and 'right' values on 'caption-side' have been removed.

C.2.113 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.2.114 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.2.115 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.2.116 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.2.117 Section 17.5.3 Table height algorithms

The 'height' property on tables is now treated as a mininimum height; the UA no longer has the option of using 'height' to constrain the size of the table to be smaller than its contents.

Percentage heights on table cells, rows, and row groups now compute to 'auto'.

The baseline of a cell is now defined much more precisely.

Defined the baseline of a row with no baseline-aligned cells.

C.2.118 17.5.4 Horizontal alignment in a column

The <string> value for 'text-align' is not part of CSS 2.1.

C.2.119 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.2.120 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.2.121 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.2.122 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.2.123 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.2.124 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.2.125 Chapter 12 Generated content, automatic numbering, and lists

The 'marker' value for 'display' does not exist in CSS 2.1

C.2.126 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.2.127 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.2.128 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.2.129 Appendix A Section 7 Mixing properties

The keywords 'mix' and 'repeat' may now appear in either order.

C.2.130 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 [3066].

C.2.131 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 preceeded 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 96 dpi device, not 90 dpi. The visual angle is thus about 0.0213 degrees instead of 0.0227, and a pixel at arm's length is about 0.26 mm 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

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 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

Changedvarious 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 don't 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

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 doesn't 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 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.3.38 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.3.39 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 and border 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 or border area of the element.

C.3.40 Section 15.2

In bullet 2, changed "the UA uses the 'font-family' descriptor" to "the UA uses the 'font-family' property".

C.3.41 Section 15.7 Font size

The statement "Negative values are not allowed" for 'font-size' now applies to percentages as well as lengths.

C.3.42 Section 16.1 Indentation

Corrected 'text-indent' to apply to table cells (and inline blocks) as well as block-level elements.

C.3.43 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.3.44 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.3.45 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.3.46 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.3.47 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.3.48 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.3.49 Section 17.6.1 The separated borders model

In the image, changed "cell-spacing" to "border-spacing".

C.3.50 Section 18.2

For the 'ButtonHighlight' value, changed the description from "Dark shadow" to "Highlight color".

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 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 definition for 'ignore'.

Added definition for 'HTML user agent'.

Added definition for 'property'.

C.4.4 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.4.5 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.4.6 Section 4.1.3 Characters and case

Clarified that when a CRLF pair terminates an escape sequence, the pair is treated as a single whitespace character as corrected in the tokenization rules.

C.4.7 Section 4.1.7 Rule sets, declaration blocks, and selectors

Replaced the term "{}-block" with "declaration block".

C.4.8 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.4.9 Section 4.3.1 Integers and real numbers

Clarified that '-0' is equivalent to '0' and is not a negative number.

C.4.10 Section 4.3.2 Lengths

Clarified that negative length values on properties that don't allow them cause the declaration to be ignored.

C.4.11 Section 4.3.4 URLs and URIs

Reduced unnecessary discussion of what a URI is.

C.4.12 Section 5.1 Pattern matching

Added note about terminology change ("simple selector") between CSS2 and CSS3.

C.4.13 Section 5.7 Adjacent sibling selectors

Clarified that text nodes and comments do not affect whether a sibling selector matches.

C.4.14 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.4.15 Section 5.9 ID selectors

Added a note that it depends on the document format which attributes are ID attributes.

C.4.16 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.4.17 Section 5.11.4 The language pseudo-class: :lang

Added a note to show the differences between ':lang(xx)' and '[lang=xx]'.

C.4.18 Section 5.12.2 The :first-letter pseudo-element

Clarified that digits can also be first letter.

C.4.19 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.4.20 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.4.21 Section 6.3 The @import rule

Except @charset from the statement that @imports must precede all other rules.

C.4.22 6.4 The Cascade

Obfuscated note about system settings and UA limitations.

C.4.23 6.4.1 Cascading order

Various editorial changes to clarify sort order.

C.4.24 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.4.25 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.4.26 Section 7.3 Recognized media types

Added text to clarify that media types are mutually exclusive, but a UA can render simulatenously to canvases with different media types.

C.4.27 Section 7.3.1 Media groups

Split "aural" media group into "audio" and "speech".

C.4.28 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.4.29 Section 8.3 Margin properties

Added a sentence to note that vertical margins have no effect on non-replaced inline elements.

C.4.30 Section 8.3.1

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.