YSlow analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages.
http://yslow.org is the official open source website.
As of Firefox 33, Venkman *no longer works*, as the APIs which it needs have been removed.
CodeBurner is a Firefox add-on that integrates with Firebug, to extend it with reference material for HTML and CSS.
Finds HTML elements matching chosen CSS selector(s) or XPath expression
Firecookie is an extension for Firebug that makes possible to view and manage cookies in your browser
Firecookie is part of Firebug since Firebug 1.10
Inline Code Finder is an add-on to Firebug, to be able to find HTML elements with any of the below issues:
* Inline style
Detailed description can be found athttp://www.robertnyman.com/inli...
Symfony Web Debug Toolbar for Firebug. Seamless Symfony debugging inside the popular Firebug.
Collections are groups of related add-ons that anyone can create and share.Explore Collections