YSlow analyzes web pages and tells you why they're slow based on Yahoo's rules for high performance web sites. This is a very handy addon to the webmasters and testers.
YSlow gives you :
* Performance report card
* HTTP/HTML summary
* List of components in the page
* Tools including JSLint
https://addons.mozilla.org/en-US/firefox/downloads/file/18173/yslow__45_0.7.1__45_fx.xpi
