Greasemonkey allows you to customize the way a webpage displays using small bits of JavaScript.
Hundreds of scripts, for a wide variety of poular sites, are already available.
You can write your own scripts, too. Mark Pilgrim's definitive Greasemonkey guide, diveintogreasemonkey.org will show you how.
Product's homepage
Requirements:
· Mozilla Firefox
What's New in This Release: [ read full changelog ]
Enhancements:
· When the toolbar is in text-only mode, the "Greasemonkey" label on the toolbar button will be striked-out when Greasemonkey is disabled. (#1544)
· When selecting a script editor, the previous choice will be remembered and displayed. (#1546)
Bug fixes:
· A change in 0.9.19 broke setTimeout() for a variety of cases, that has been reverted. (#1549, #1552, #1553)