::before ::after什么意思?

Question

RT, html代码里出现这个::after,  这是什么意思呢? 用来干嘛的?

Answer 1

::before,::after 伪元素 :before,:after 伪类

Answer 2

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Answer 3

伪类，为某个元素前后添加内容

Answer 4

http://www.imooc.com/code/4409《十天精通CSS3》课程里有详细的介绍^_^

Answer 5

伪类，就是before、after。也就是前和后加一个类