YSlow : Firefox add-on by Yahoo! Inc

YSlow analyzes web pages and tells you why they're slow based on Yahoo's rules for high performance web sites.

YSlow gives you:

• Performance report card
• HTTP/HTML summary
• List of components in the page
• Tools including JSLint
  

YSlow is licensed under the Mozilla Public License (MPL) version 1.1, with portions licensed by third parties under other license terms.

To review the terms before installing, see :
http://developer.yahoo.com/yslow/faq.html#faq_license.

You must install Firebug to enable YSlow.