A W3C announcement describes the release of three Cascading Style Sheets (CSS) language specifications as Candidate Recommendations.
The Cascading Style Sheets, Level 2 Revision 1. CSS 2.1 Specification "allows authors and users to attach style to structured documents; 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 and 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." This specification will remain at Candidate Recommendation level at least until September 2004.
CSS Print Profile "specifies a conformance profile for printing from mobile devices to low-cost printers, identifying a minimum set of properties, values, selectors, and cascading rules. This profile was designed in conjunction with XHTML-Print for low cost printers that may not have a full-page buffer and that generally print from top-to-bottom and left-to-right with the paper in a portrait orientation."
The CSS3 Paged Media Module "describes the page model that partitions a flow into pages. It builds on the CSS3 Box model module and introduces and defines the page model and paged media. It adds functionality for pagination, page margins, headers and footers, image orientation. Finally, it extends generated content for the purpose of cross-references with page numbers."
Bibliographic Information and Overview
Cascading Style Sheets, Level 2 Revision 1. CSS 2.1 Specification. W3C Candidate Recommendation 25-February-2004. Edited by Bert Bos, Tantek Çelik, Ian Hickson, and Håkon Wium Lie. Version URL: http://www.w3.org/TR/2004/CR-CSS21-20040225. Latest version URL: http://www.w3.org/TR/CSS21. Previous version URL: http://www.w3.org/TR/2003/WD-CSS21-20030915.
"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. CSS2.1 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 stylesheet is necessarily forwards-compatible with CSS 2.1, it is the case that a stylesheet 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..." [from Section 1.1, CSS 2.1 vs CSS 2]
CSS Print Profile. W3C Candidate Recommendation 25-February-2004. Edited by Jim Bigelow (Hewlett-Packard Company). Version URL: http://www.w3.org/TR/2004/CR-css-print-20040225. Latest Version URL: http://www.w3.org/TR/css-print. Previous Version URL: http://www.w3.org/TR/2003/WD-css-print-20031218.
"CSS21 specifies how developers can author style sheets for presenting documents across multiple devices and media types. While this is very important, it is also important that authors have an understanding of what features are supported on these different devices. Likewise, it is important that similar devices operate in a similar manner. Otherwise, authors will need to develop style sheets for each version of each device — raising the cost of content development and decreasing interoperability.
The CSS Print Profile specifies a conformance profile for printing from mobile devices to low-cost printers, identifying a minimum set of properties, values, selectors, and cascading rules. This profile was designed in conjunction with XHTML-Print for low cost printers that may not have a full-page buffer and that generally print from top-to-bottom and left-to-right with the paper in a portrait orientation.
This profile also contains an enhanced layout extension set that is the companion of the XHTML-Print extension set and supports more exacting page layouts and orientations. The enhanced layout extension may require full page buffering within the printer. Conformance to this profile means that a user agent supports, at a minimum, the features defined in this specification..." [from the Overview]
CSS3 Paged Media Module. W3C Candidate Recommendation 25-February-2004. Edited by Håkon Wium Lie (Opera Software) and Jim Bigelow (Hewlett-Packard Company). Version URL: http://www.w3.org/TR/2004/CR-css3-page-20040225. Latest version URL: http://www.w3.org/TR/css3-page. Previous version URL: http://www.w3.org/TR/2003/WD-css3-page-20031218/.
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, CSS3 describes how:
- page breaks are created
- the page size, margins, border, and padding are specified
- headers and footers are established within the page margins
- content such as page counters and string-sets placed in the headers and footers
CSS3 defines a page model that specifies how a document is formatted within a rectangular area, called the page box, that has finite width and height. The page box does not necessarily have a one-to-one correspond to the real sheet where the document will ultimately be rendered (paper, transparency, screen etc.). The CSS3 page model specifies formatting within the page box, but it is the user agent's responsibility to transferred the page box to the sheet. Some user agent transfer possibilities that are not addressed by CSS3 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
Although CSS3 does not specify how user agents transfer page boxes to sheets, it does include certain mechanisms for telling user agents about the page sheet size and orientation. Furthermore, CSS3 assumes that one page box will be transfer to a side of a sheet..." [from the Introduction]
- Cascading Style Sheets, Level 2 Revision 1. CSS 2.1 Specification
- CSS Print Profile
- CSS Print Profile Implementation Report
- CSS3 Paged Media Module
- W3C news item
- Cascading Style Sheets Roadmap (specifications under development)
- W3C CSS Validation Service
- W3C Web Style Sheets home page
- W3C Cascading Style Sheets home page
- Mail Archives for W3C public list 'email@example.com'. "This mailing list is for technical discussion on Web Style Sheets. This is a focused discussion area: all posts to this list must be about style sheets. The list is also the preferred place for discussing working drafts that are published by W3C's working group on CSS (Cascading Style Sheets)."
- "W3C Cascading Style Sheets" - Main reference page.