Why is my web page slow? YSlow for Firebug can tell you.
Posted by Shane O'Sullivan on July 25, 2007
Yahoo have released a very useful extension for Firebug, which is itself an extension for Firefox, which can be used to analyze a web page’s performance. The extension, called YSlow, appears as a separate pane in Firebug, and gives you a whole load of statistics about your page.
However, in addition to the bare numbers, it also gives your page a ranking, from zero to a hundred, and offers tips in plain English on you can improve the performance of your page.
All in all, a very handy little addition to a web developer’s toolkit.