提高网页效率的准则及其测试工具

如何提高网页的效率（上篇）——提高网页效率的14条准则
    *  Make Fewer HTTP Requests
    * Use a Content Delivery Network
    * Add an Expires Header
    * Gzip Components
    * Put CSS at the Top
    * Move Scripts to the Bottom
    * Avoid CSS Expressions
    * Make JavaScript and CSS External
    * Reduce DNS Lookups
    * Minify JavaScript
    * Avoid Redirects
    * Remove Duplicate Scripts
    * Configure ETags
    * Make Ajax Cacheable

如何提高网页的效率（下篇）——Use YSlow to know why your web Slow