What is the principle of css pseudo-class

css pseudo-class principle means that pseudo-classes classify elements based on characteristics, rather than their names, attributes or content; in principle, characteristics cannot be inferred from the document tree. In the sense Pseudo-classes can be dynamic, and an element can gain or lose a pseudo-class as the user interacts with the document.

The operating environment of this tutorial: windows7 system, css3 version. This method is suitable for all brands of computers.

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What is the principle of css pseudo-classes?

Explanation: Pseudo-classes classify elements based on characteristics rather than their names, attributes or content;

In principle, characteristics cannot be inferred from the document tree owned. Pseudo-classes can feel dynamic, and an element can gain or lose a pseudo-class as the user interacts with the document.

The exceptions are ":first-child" which can be inferred from the document tree, and ":lang" which is also inferred from the document tree in some cases.

Pseudo-classes include: :first-child, :link:, vistited, :hover:, active:focus, :lang

What are pseudo-classes?

It means that the css itself gives it some features and functions, that is, you don’t need class=... or id=..., you can use it directly, and of course you can also change it. Some attributes such as: a:link{color:#ff0000;}

Many CSS suggestions are not supported by browsers, but there are four pseudo-classes for connections that can be used safely. They are link, visited, hover and active respectively.

a:link{color:#000000;} /*设置 a 对象在未被访问前的样式。*/
a:hover{color:#000000;} /*设置对象在其鼠标悬停时的样式。*/
a:active{color:#000000;} /*设置对象在被用户激活(在鼠标点击与释放之间发生的事件)时的样式。*/
a:visited{color:#000000;} /*设置 a 对象在其链接地址已被访问过时的样式。*/

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