百度前端技术学院Html&CSS学习资源
https://www.zhihu.com/question/22689579
https://developer.mozilla.org/zh-CN/docs/Web/Guide/HTML/Introduction
http://www.imooc.com/learn/9
https://developer.mozilla.org/zh-CN/docs/Web/Guide/HTML/Introduction
https://developer.mozilla.org/zh-CN/docs/Web/Guide/CSS/Getting_started
http://www.imooc.com/learn/9
https://developer.mozilla.org/zh-CN/docs/Web/CSS/position
https://developer.mozilla.org/en-US/docs/Web/CSS/float
Learn CSS Positioning in Ten Steps:
http://www.barelyfitz.com/screencast/html-training/css/positioning/
http://zh.learnlayout.com/clearfix.html
StackOverflow:Which method of ‘clearfix’ is best?
http://stackoverflow.com/questions/211383/which-method-of-clearfix-is-best
http://www.w3cplus.com/css/advanced-html-css-lesson2-detailed-css-positioning.html
Centering in CSS: A Complete Guide
https://css-tricks.com/centering-css-complete-guide/
Get HTML & CSS Tips In Your Inbox
http://howtocenterincss.com/