CSS

https://www.w3cplus.com/blog/tags/368.html

https://codepen.io/

https://developer.mozilla.org/zh-CN/docs/Web/CSS/CSS_Box_Model/Mastering_margin_collapsing

http://lesscss.cn/

https://github.com/yui/yui3/blob/master/src/cssreset/css/cssreset.css

https://www.zhihu.com/question/25147729

http://blog.csdn.net/huang100qi/article/details/44304159