This specification defines Cascading Style Sheets, level 2
revision 1 (CSS 2.1). CSS 2.1 is a style sheet language
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
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. Implementations may refer to CSS2 for the
definitions of features that have been removed, but for other features
CSS 2.1 is the normative reference.
Status of this document
This section describes the status of this document at the time
of its publication. Other documents may supersede it. 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 is a "Last Call" Working Draft. The deadline for comments is 15 July 2005.
public mailing list firstname.lastname@example.org (see instructions) is preferred for discussion of
this and other specifications in the Style area. When commenting on
this document, please put the text "CSS21" in the subject, preferably
like this: "[CSS21] <summary of comment>"
Publication as a Working Draft does not imply endorsement by the
W3C Membership. It is inappropriate to cite this document as other
than work in progress.
A test suite and a report on implementations will be provided
before the document becomes a Proposed Recommendation.
For this specification to exit the CR stage, the following
conditions must be met:
There must be at least two interoperable implementations
for every feature. For the purposes of this criterion,
we define the following terms:
A section or subsection of the specification.
passing the respective test cases in the test suite, or,
if the implementation is not a web browser, equivalent tests.
Every relevant test in the test suite should have an equivalent
test created if such a UA is to be used to claim interoperability.
In addition if such a UA is to be used to claim interoperability,
then there must one or more additional UAs which can also pass
those equivalent tests in the same way for the purpose of
interoperability. The equivalent tests must be made publicly
available for the purposes of peer review.
a user agent which:
implements the feature.
is available (i.e. publicly downloadable or available
through some other public point of sale mechanism). This is the
"show me" requirement.
is shipping (i.e. development, private or unofficial
versions are insufficient).
is not experimental (i.e. is intended for a wide audience
and could be used on a daily basis).
A minimum of six months of the CR period must have elapsed.
This is to ensure that enough time is given for any remaining major
errors to be caught.
The CR period will be extended if implementations are slow to
Features that were not in CSS1 will be dropped (thus reducing the
list of "all" features mentioned above) if two or more
interoperable implementations of those features are not found by
the end of the CR period.
Features will also be dropped if sufficient and adequate
tests (by judgment of the working group) have not been produced for
those features by the end of the CR period.
Features at risk
The working group has identified the following features as being
currently poorly implemented by UAs. They are therefore most at risk
of being removed from CSS 2.1 when exiting CR. (Any changes of this
nature will still result in the specification being returned to last
call.) Implementors are urged to implement these features, or correct
bugs in their implementations, if they wish to see thsse features remain
in this specification.
New 'list-style-type' values
Implementors should look at CSS3 Lists instead, where these and
many other new values not found in CSS1 are defined in detail.
Support for multiple ID attributes for the ID selector
Because implementations are not expected to support multiple IDs
per element soon, this feature may be made informative. The W3C
Selectors specification will continue to have this feature
Automatic table layout algorithm
The input to the suggested (non-normative) automatic layout
algorithm for tables is restricted to (1) the containing block width
and (2) the content and properties of the table and its
children. This restriction may be lifted.
The 'quotes' property and the
'open-quote', 'close-quote', 'no-open-quote' and 'no-close-quote'
keywords may be dropped.