1.selector:pseudo element{property:value;}
2.first-letter first-line
CSS3:: 与pseudo class 区别 old browser not do well
3.before after
property=content
4.
【CSS】Intermediate7:Pseudo Elements,布布扣,bubuko.com
【CSS】Intermediate7:Pseudo Elements
原文：http://www.cnblogs.com/yzhen/p/3660012.html