Movatterモバイル変換

Abstract

This specification defines Cascading Style Sheets, level 2revision 1 (CSS 2.1). CSS 2.1 is a style sheet languagethat allowsauthors and users to attach style (e.g., fonts and spacing) tostructured documents (e.g., HTML documents and XMLapplications). By separating the presentation style of documents fromthe content of documents, CSS 2.1 simplifies Web authoring andsite maintenance.

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

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

Status of this document

This section describes the status of this document at the timeof its publication. Other documents may supersede it. A list ofcurrent W3C publications and the latest revision of this technicalreport can be found in theW3Ctechnical reports index at http://www.w3.org/TR/.

This is a W3C Candidate Recommendation, which means thespecification has been widely reviewed and W3C recommends that it beimplemented. It will remain Candidate Recommendationat least until 1 September 2004.

Publication as a Candidate Recommendation does not implyendorsement by the W3C Membership. It is inappropriate to cite thisdocument as other than work in progress.

A test suite and a report on implementations will be providedbefore the document becomes a Proposed Recommendation.

The (archived)public mailing listwww-style@w3.org (seeinstructions) is preferredfor discussion of this and other specifications in the Style area.When commenting on this document, please put the text "CSS21" in thesubject, preferably like this: "[CSS21] <summary of comment>"

This document is produced by theCSS working group (part oftheStyle Activity, seesummary).

Patent disclosures relevant to CSS may be found on the WorkingGroup's publicpatent disclosurepage.

Candidate Recommendation Exit Criteria

For this specification to exit the CR stage, the followingconditions must be met:

1. There must be at least two interoperable implementations for every feature. For the purposes of this criterion, we define the following terms:

   feature

   A section or subsection of the specification.

   interoperable

   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.

   implementation

   a user agent which:

   1. implements the feature.
   2. is available (i.e. publicly downloadable or available through some other public point of sale mechanism). This is the "show me" requirement.
   3. is shipping (i.e. development, private or unofficial versions are insufficient).
   4. is not experimental (i.e. is intended for a wide audience and could be used on a daily basis).

2. 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.

3. The CR period will be extended if implementations are slow to appear.

4. 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.

5. 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.