CSS2 ambitions precipitated
To meet the first specification does not cover even CSS1, CSS is assigned in 1997 to a new working group at W3C, chaired by Chris Lilley. In 2007, this group shall include representatives from Apple, Google, IBM, Microsoft, Adobe, Mozilla Foundation and Opera.
Published as a recommendation in May 1998, the second level of CSS considerably extends the theoretical possibilities of cascading style sheets, especially with about 70 additional properties. At the typographic layout of text in addition initiated with CSS1 end:
- Declination in styles specific to different media in which a web page can be restored (print, delivered by a speech synthesizer, a Braille device, a projection device, a mobile, etc.).
- New positioning properties to the screen to enable the realization of advanced layout, from a document developed jointly by Microsoft and Netscape
- A set of properties allowing the downloading of fonts specific
- New properties to involve the user preferences in the shaping of a site.
However, this feature-rich will only have limited coverage in its implementations:
- The declination media is partly a failure: the vocal style renderings are lack of theoretical consideration by voice browsers and screen readers. They are otherwise incompatible with the standard interaction SSML. It is the same display and printing Braille. The print styles are only very partially adopted by the graphical browsers, while some mobile browsers to ignore as the early 2000s the CSS media type that is dedicated to them.
- Only a few advanced positioning properties are recognized by all graphical browsers, thereby consolidating the practical layout based on deflections of CSS features (or floating block system set) and HTML (tables layouts).
- The download fonts raises implementations and divergent between Netscape and Internet Explorer, and is opposed by publishers fonts, anxious to protect their business interests.
Several reasons are cited for these difficulties and slow implementations of CSS2:
- “Under-specification ofcertain sections”. Håkon Lie himself stresses in his thesis on cascading style sheets, in 2005, the risk of loss or non-implementation of interoperability relating to “excessive features, such as markers of the list, cutting marks for printing or downloading of fonts. Similarly, the complexity of advanced selectors is difficult to reconcile with the management of the waterfall.
- The lack of interest from manufacturers of browsers for functionality that did not necessarily fit their strategic or commercial objectives.
- Discontinuation of development of the Internet Explorer browser dominating the market, from 2001 to 2006. Håkon Lie Leo wrote in 2005: “2001 was a turning point for CSS. That was the year Microsoft Internet Explorer 6.0 product which provides a support functional, though incomplete and buggy, CSS. No other browser has been able to compete Winie in terms of number of users. Winie has, therefore, determined the subset of CSS used by the authors. The limited support of CSS Winie, combined with a de facto monopoly in web browser, is currently the most serious problem of deployment of CSS.
CSS 2.1, return to implementations
Returns implementation of CSS2 lead the working group to draft W3C CSS from 2001 a revised CSS 2.1 (CSS Level 2 Revision 1 “), based on what was actually adopted by different browsers . The objectives of this review are:
- Maintain compatibility with those portions of CSS2 that are widely accepted and implemented.
- Incorporated in the standard CSS2 errata all previously published.
- When the implementations are very different from the CSS2 specification, change the specification for it is consistent with generally accepted practices.
- Remove CSS2 features which have been rejected by the CSS community, given their lack of implementation. CSS 2.1 aims to reflect the CSS mechanisms have been reasonably widely implemented for HTML and XML in general (rather than a particular XML language, or HTML only).
- • Remove the mechanisms that will CSS2 obsoleted by CSS3, and thus encourage the adoption of CSS3 mechanisms in place.
- • Add a (very) small number of new property values, when implementation experience has shown that they were responding to a need for implementing CSS2.
CSS2 CSS 2.1 corrects many points of detail, remove some sections in whole or part (vocal styles set the media type in “aural, print styles, downloadable fonts, whose definitions are pushed more evidence the future CSS3), and the explicit findings from updated at implementations (the advanced management of blocks floating through the “formatting contexts”).
After hitting eight successive drafts, CSS 2.1 is a Candidate Recommendation in July 2007, that is to say the standard to be followed by implementations.
In 2007, no browser has indeed completed the integration of CSS 2.1: it would be implemented to 56% from the Internet Explorer 7, Firefox 2 by 91% and 94% by Opera 9 . Moreover, only a portion of graphical browsers have passed or retained as an objective the Acid2 test, launched in 2005 by the Web Standards Project, the initiative Håkon Lie, to promote the implementation of a particular choice of CSS 2.1 features regarded as the main advances needed: positioning of elements in the display, generalization of the model rendering table to all elements, generated content using CSS. The business use of CSS is therefore limited to an arbitrary subset thereof, determined by the common implementations.
The development of the third level of cascading style sheets began in 1999, alongside that of CSS 2.1.
CSS3 is “modular” to facilitate its updates, but its implementation by user agents, capabilities and needs of increasingly diverse (graphical browsers, mobile browsers, voice browsers). Browsers can then implement subsets of CSS3.
Therefore, the degree of progress varies CSS3 modules and the degree of priority given to them by the CSS Working Group . In 2007, the most advanced modules (candidate recommendations) concerning the formatting ruby annotations, negotiating style between servers and user agents (“Media Queries”), rendering Web TV, color management or decision into account the configuration of the user interface.
Study: From Wikipedia, the free encyclopedia. The text is available under the Creative Commons.
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