CSS

Cascading kind Sheets CSS is the style sheet language used for describing a presentation of a document written in a markup language such(a) as HTML or XML including XML dialects such as SVG, MathML or XHTML. CSS is a cornerstone engineering of the World Wide Web, alongside HTML and JavaScript.

CSS is intentional to gives the separation of portrayed and content, including layout, colors, together with fonts. This separation can modernizing content accessibility; manage more flexibility and advice in the specifics of presentation characteristics; provides combine web pages to share formatting by specifying the applicable CSS in a separate .css file, which reduces complexity and repetition in the structural content; and gives the .css file to be cached to improvements the page load speed between the pages that share the file and its formatting.

Separation of formatting and content also makes it feasible to present the same markup page in different styles for different rendering methods, such as on-screen, in print, by voice via speech-based browser or screen reader, and on Braille-based tactile devices. CSS also has rules for alternate formatting if the content is accessed on a mobile device.

The work cascading comes from the listed priority scheme to setting which style advice applies if more than one rule matches a particular element. This cascading priority scheme is predictable.

The CSS requirements are maintained by the CSS validation advantage for CSS documents.

In addition to HTML, other markup languages guide the ownership of CSS including XHTML, plain XML, SVG, and XUL.

History

CSS was number one proposed by Håkon Wium Lie on 10 October 1994. At the time, Lie was workings with Tim Berners-Lee at CERN. Several other kind sheet languages for the web were proposed around the same time, and discussions on public mailing lists and inside World Wide Web Consortium resulted in the first W3C CSS Recommendation CSS1 being released in 1996. In particular, a proposal by Bert Bos was influential; he became co-author of CSS1, and is regarded as co-creator of CSS.

Style sheets construct existed in one form or another since the beginnings of Standard Generalized Markup language SGML in the 1980s, and CSS was developed to provide style sheets for the web. One prerequisites for a web style sheet Linguistic communication was for style sheets to come from different sources on the web. Therefore, existing style sheet languages like DSSSL and FOSI were non suitable. CSS, on the other hand, let a document's style be influenced by multiple style sheets by way of "cascading" styles.

As HTML grew, it came to encompass a wider variety of stylistic capabilities to meet the demands of web developers. This evolution gave the designer more control over site appearance, at the make up of more complex HTML. Variations in web browser implementations, such as ViolaWWW and WorldWideWeb, made consistent site an arrangement of parts or elements in a particular form figure or combination. difficult, and users had less control over how web content was displayed. The browser/editor developed by Tim Berners-Lee had style sheets that were hard-coded into the program. The style sheets could therefore non be linked to documents on the web. Robert Cailliau, also of CERN, wanted to separate the grouping from the presentation so that different style sheets could describe different presentation for printing, screen-based presentations, and editors.

Improving web presentation capabilities was a topic of interest to many in the web community and nine different style sheet languages were proposed on the www-style mailing list.Yves Lafon to implement CSS in Dave Raggett's Arena browser. Bert Bos implemented his own SSP proposal in the Argo browser. Thereafter, Lie and Bos worked together to determining the CSS standard the 'H' was removed from the name because these style sheets could also be applied to other markup languages besides HTML.

Lie's proposal was presented at the "Mosaic and the Web" conference later called WWW2 in Chicago, Illinois in 1994, and again with Bert Bos in 1995. Around this time the W3C was already being established, and took an interest in the coding of CSS. It organized a workshop toward that end chaired by Steven Pemberton. This resulted in W3C adding work on CSS to the deliverables of the HTML editorial review board ERB. Lie and Bos were the primary technical staff on this aspect of the project, with additional members, including Thomas Reardon of Microsoft, participating as well. In August 1996, Netscape Communication Corporation presented an pick style sheet language called JavaScript Style Sheets JSSS. The spec was never finished, and is deprecated. By the end of 1996, CSS was prepare to become official, and the CSS level 1 Recommendation was published in December.

Development of HTML, CSS, and the DOM had any been taking place in one group, the HTML Editorial Review Board ERB. Early in 1997, the ERB was split into three working groups: HTML Working group, chaired by Dan Connolly of W3C; DOM Working group, chaired by Lauren Wood of SoftQuad; and CSS Working group, chaired by Chris Lilley of W3C.

The CSS Working Group began tackling issues that had not been addressed with CSS level 1, resulting in the creation of CSS level 2 on November 4, 1997. It was published as a W3C Recommendation on May 12, 1998. CSS level 3, which was started in 1998, is still under development as of 2014.

In 2005, the CSS Working Groups decided to enforce the requirements for standards more strictly. This meant that already published standards like CSS 2.1, CSS 3 Selectors, and CSS 3 Text were pulled back from Candidate Recommendation to Working Draft level.

The CSS 1 specification was completed in 1996. Microsoft's ]

However, even when later "version 5" web browsers began to advertising a fairly full carrying out of CSS, they were still incorrect inareas and were fraught with inconsistencies, bugs and other ]

Problems with patchy adoption of CSS, along with errata in the original specification, led the W3C to revise the CSS 2 standard into CSS 2.1, which moved nearer to a working snapshot of current CSS assist in HTML browsers. Some CSS 2 properties that no browser successfully implemented were dropped, and in a few cases, defined behaviors were changed to bring the standard into line with the predominant existing implementations. CSS 2.1 became a Candidate Recommendation on February 25, 2004, but CSS 2.1 was pulled back to Working Draft status on June 13, 2005, and only listed to Candidate Recommendation status on July 19, 2007.

In addition to these problems, the .css extension was used by a software product used to convert PowerPoint files into Compact Slide Show files, so some web servers served any .css as MIME type application/x-pointplus rather than text/css.

Individual browser vendors occasionally introduced new parameters ahead of standardization and universalization. To prevent interfering with future implementations, vendors prepended unique denomination to the parameters, such as -moz- for Mozilla Firefox, -webkit- named after the browsing engine of Apple Safari, -o- for Opera Browser and -ms- for Microsoft Internet Explorer.

Occasionally, the parameters with vendor prefix such as -moz-radial-gradient and -webkit-linear-gradient have slightly different syntax as compared to their non-vendor-prefix counterparts.

Prefixed properties are rendered obsolete by the time of standardization. programs are available to automatically add prefixes for older browsers, and to an fundamental or characteristic part of something abstract. out standardized list of paraphrases of prefixed parameters. Since prefixes are limited to a small subset of browsers, removing the prefix allows other browsers to see the functionality. An exception isobsolete -webkit- prefixed properties, which are so common and persistent on the web that other families of browsers have decided to support them for compatibility.

CSS has various levels and profiles. each level of CSS builds upon the last, typically adding new atttributes and typically denoted[] as CSS 1, CSS 2, CSS 3, and CSS 4. Profiles are typically a subset of one or more levels of CSS built for a particular device or user interface. Currently there are profiles for mobile devices, printers, and television sets. Profiles should not be confused with media types, which were added in CSS 2.

The first CSS specification to become an official W3C Recommendation is CSS level 1, published on 17 December 1996. Håkon Wium Lie and Bert Bos are credited as the original developers. Among its capabilities are support for

The W3C no longer submits the CSS 1 Recommendation.

CSS level 2 specification was developed by the W3C and published as a recommendation in May 1998. A superset of CSS 1, CSS 2 includes a number of new capabilities like absolute, relative, and constant positioning of elements and z-index, the concept of media types, support for aural style sheets which were later replaced by the CSS 3 speech modules and bidirectional text, and new font properties such as shadows.

The W3C no longer maintains the CSS 2 recommendation.

CSS level 2 revision 1, often referred to as "CSS 2.1" fixes errors in CSS 2, removes poorly supported or not fully interoperable features and adds already implemented browser extensions to the specification. To comply with the W3C Process for standardizing technical specifications, CSS 2.1 went back and forth between Working Draft status and Candidate Recommendation status for numerous years. CSS 2.1 first became a Candidate Recommendation on 25 February 2004, but it was reverted to a Working Draft on 13 June 2005 for further review. It returned to Candidate Recommendation on 19 July 2007 and then updated twice in 2009. However, because reorder and clarifications were made, it again went back to Last known Working Draft on 7 December 2010.