BFC模式

1.入门理解

http://www.cnblogs.com/dojo-lzz/p/3999013.html#undefined

2.关于清楚浮动、包含浮动的理解

http://www.cnblogs.com/dolphinX/p/3508869.html

3.官网文档

https://www.w3.org/TR/CSS21/visuren.html#block-formatting