Firebug Software:

Firebug Software:

It integrates with Firefox to put a wealth of web development tools at users fingertips while user browse. Users can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.

http://getfirebug.com/

Firebug is free and open source; it is licensed under the BSD license.

Firebug was initially written by Joe Hewitt, in January 2006. 

The Firebug Working Group oversees the open source development and extension of Firebug. 

It has two major implementations: an extension (add-on) for Mozilla Firefox and a bookmark implementation called Firebug Lite.A cross-browser version is in development. 

Currently, the Firebug add-on has over 3+ million active daily users.