css2.1 was officially released in February 2004; css2.1 is the first revision of the second level of CSS. It is built on CSS2, which is built on CSS1; it supports the style of specified media tables, so authors can customize how their documents appear on visual browsers, auditory devices, printers, braille devices, handheld devices, etc.; it also supports content positioning, table layout, internationalization, and user interface-related properties.
The operating environment of this tutorial: Windows 10 system, CSS3 version, DELL G3 computer
When was css2.1 proposed? ?
February 2004.
Since its development, CSS has gone through a total of 4 versions of iterations:
1) CSS1.0
In December 1996, W3C released CSS The first version - CSS1.0 (https://www.w3.org/TR/CSS1/).
2) CSS2.0
In May 1998, CSS2.0 version was officially released (https://www.w3.org/TR/CSS2/).
3) CSS2.1
In February 2004, CSS2.1 was officially released. This version is slightly modified based on CSS2.0 and deletes many attributes that are not supported by browsers.
4) CSS3
As early as 2001, the W3C started preparing to develop the third version of CSS, which has not been finalized so far. Although the complete CSS3 standard has not yet been released, major browsers have begun to support most of its features.
CSS2.1 Introduction:
CSS2.1 is the first revision of the second level of CSS (Cascading Style Sheets), which is built on CSS2, which Built on CSS1. It supports media-specific style sheets, so authors can customize how their documents appear on visual browsers, hearing devices, printers, Braille devices, handheld devices, and more. It also supports content positioning, table layout, internationalization, and user interface-related properties.
CSS2.1 corrects some errors in CSS2 (the most important is the redefinition of the height/width of absolutely positioned elements, the HTML "style" attribute and the recalculated 'clip' attribute, which has a greater impact ), and adds some already widely implemented features. But CSS 2.1 is a "snapshot" of evolving CSS: it contains all features that have been implemented before the release recommendation date.
CSS2.1 is intended to replace CSS2. Some parts of CSS2 have not changed in CSS2.1, some have been modified, and some have been deleted. The removed parts reappear in the CSS3 specification.
Recommended learning: "css video tutorial"
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