网站性能提高
1减少http请求
https://developer.mozilla.org/cn/Canvas_tutorial/Using_imageshttp://www.ericstory.me/2010/01/%E9%9D%99%E6%80%81%E6%96%87%E4%BB%B6%E6%89%93%E5%8C%85%E5%92%8C%E8%87%AA%E5%8A%A8%E6%97%B6%E9%97%B4%E6%88%B3/
http://www.aoao.org.cn/blog/2010/04/js-resource-packages/
http://en.wikipedia.org/wiki/Data:_URL
2）使用YSlow工具分析网站效率
http://www.online-tech-tips.com/web-site-tips/use-yslow-firefox-add-on-to-analyze-the-performance-of-your-web-site/zh/