http://blog.csdn.net/aiolos1111/article/details/51880223
http://www.jianshu.com/p/a5d194a429b6
http://blog.csdn.net/tongseng/article/details/52788598
http://www.cnblogs.com/samwu/p/5341056.html
http://www.zhangxinxu.com/wordpress/2012/09/new-viewport-relative-units-vw-vh-vm-vmin/
http://www.360doc.com/content/16/0810/17/16915_582277274.shtml
http://yunkus.com/physical-pixel-device-independent-pixels/