Firebug

Firebug is an extension for Mozilla Firefox which allows déboguer, to publish and modify HTML, the CS and the Javascript of a Web page.

Firebug was developed by Joe Hewitt, one of the creators of Firefox.
Cette extension was placed at the disposal under license MPL

The development of Firebug is actively supported by Yahoo.

See too

YSlow is an extension developed by Yahoo making it possible to measure and test various indicators relating to the speed of remote loading and posting of a Web page. This extension is integrated into Firebug to function.

External bonds

https://addons.mozilla.org/en-US/firefox/addon/1843
http://www.getfirebug.com
Firebug Development Blog

Random links: