PUBLIC MARKS with tags clevermarks & firebug

"The Firebug plugin that extracts embedded (Typekit) font resources from websites and allows their separate download. "

"Highlight the rendered font-family in Firebug "

Page Speed is an open-source Firefox/Firebug Add-on. Webmasters and web developers can use Page Speed to evaluate the performance of their web pages and to get suggestions on how to improve them.

FirePHP enables you to print to your Firebug Console using a simple PHP function call. What makes FirePHP different? All data is sent via a set of X-FirePHP-Data response headers. This means that the debugging data will not interfere with the content on your page. Thus FirePHP is ideally suited for AJAX development.

John J. Barton has released a new open source framework named Fireclipse that enables nice coupling of Firefox and Eclipse for debugging purposes, working on top of Firebug.

Logging PHP and JavaScript errors to same window makes debugging easier