CSS ::伪元素
CSS伪元素用于向某些选择器添加特殊效果。您无需使用JavaScript或任何其他脚本即可使用这些效果。伪元素的简单语法如下-
selector:pseudo-element {property: value}CSS类也可以与伪元素一起使用-
selector.class:pseudo-element {property: value}最常用的伪元素如下-
：第一行伪元素
下面的示例演示如何使用 ：first-line 元素向文档中的第一行元素添加特殊效果。
This line would not have any underline because this belongs to nline class.
The first line of this paragraph will be underlined as defined in the
CSS rule above. Rest of the lines in this paragraph will remain normal.
This example shows how to use :first-line pseduo element to give effect
to the first line of any HTML element.
：first-letter伪元素
下面的示例演示如何使用 ：first-letter 元素向文档中的元素的首字母添加特殊效果。
First character of this paragraph will be normal and will have font size 10 px;
The first character of this paragraph will be 5em big as defined in the
CSS rule above. Rest of the characters in this paragraph will remain
normal. This example shows how to use :first-letter pseduo element
to give effect to the first characters of any HTML element.
：before伪元素
下面的示例演示如何使用 ：before 元素在任何元素之前添加一些内容。
This line will be preceded by a bullet.
This line will be preceded by a bullet.
This line will be preceded by a bullet.
：after伪元素
下面的示例演示如何使用 ：after 元素在任何元素之后添加一些内容。
This line will be succeeded by a bullet.
This line will be succeeded by a bullet.
This line will be succeeded by a bullet.