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The World Wide Web Consortium (W3C) issued a Recommendation for Web style sheets December, 1996. The Recommendation, Cascading Style Sheets, level 1 (CSS1), gives Web designers a robust set of tools to specify Web page presentation properties such as fonts and colors.
CSS allows both authors and end users to specify style sheets and control presentation characteristics, such as font and color. Most often, end users will be happy to use the style sheets suggested by the author, but sometimes the end user will have personal preferences. For example, visually impaired users may want to use a large font with high contrast colors.
The style sheet mechanism combines the different style sheets into one presentation. In case of conflicts between the user and author style sheets, the author will have ultimate control. However, the user also can choose to turn off author style sheets.
On the Web today, it's common to make images of text in order to control fonts and colors. Images use much more bandwidth than text, and the perceived slowness of the Web can in part be attributed to this practice. CSS1, while allowing authors to express the same rich styles, is text-based so pages using CSS1 are smaller and load faster than comparable image-based pages.
By linking multiple documents -- even all documents on a site -- to one style sheet, maintaining consistent look and feel throughout a site becomes much simpler. To change the appearance of documents, like altering the background texture, changes only need to be made in one place.
While HTML extensions often replaced the document structure with purely presentational tags, CSS1 attaches style information to the document structure. Preserving document structure means that documents remain device independent, and Web search engines can do a better job indexing the documents. It also allows the same documents to be viewed on different media such as print, speech, and television.
Web designers constantly look for ways to add new effects to their documents. While the main focus of CSS1 is to establish the concept of style sheets on the Web, it also adds new formatting capabilities. For example, CSS1 allows designers to set background colors and images on a per element basis, and have text elements floating like images can float. Also, among the advanced features of CSS1 are word-spacing, letter-spacing and text justification.
For CSS1 to gain acceptance on the Web, it's important to have support in common browsers. Microsoft supports much of CSS1 in Internet Explorer 3.0 and will extend support in the upcoming 4.0 release. Netscape has announced support and the W3C expects other browsers to follow. Also, CSS1 was implemented in several non-commercial browsers, including Arena and Emacs-W3 in 1995.
Ideally, the creation of HTML+CSS is transparent for the designer. The W3C anticipates CSS1 will be supported by HTML editors and are actively working with several vendors to ensure interoperability. W3C's testbed editing environment, Amaya has an initial CSS1 implementation.
Just like word processors and DTP packages now can save documents as HTML today, the W3C expects wide support for HTML+CSS as an output format. CSS1 allows these applications to preserve more of the information in their documents. Already, Adobe's FrameMaker support this feature in HoTaMaLe.
The Web's main document format, Hypertext Markup Language (HTML), was intentionally designed as a simple language that valued document structure over document presentation. In 1994 HTML has established itself as a universal document format, but it was clear that HTML -- even with extensions -- would not fulfill authors' demands for presentational capabilities.
Work on CSS was started in October 1994 by Håkon Lie, then at CERN, the birthplace of the Web. In July 1995, work on CSS continued at INRIA, the European host of W3C, and Bert Bos joined the project. A W3C workshop on Style Sheets later that year made it clear that W3C Members wanted to work towards a common style sheet specification. The forming consensus was announced in March 1996, and commercial products based on CSS1 were out in the summer of 1996. Since then, the specification has been further refined by W3C's HTML Editorial Review Board. Also, the HTML community has contributed to the development of CSS through public mailing lists.
CSS1 defines a common syntax that will be the basis for a family of forthcoming CSS specifications. The W3C is working with its Members on specifications in the areas of printing, extended layout capabilities, speech style sheets and Web fonts.