Greasemonkey v4.13 
Allows you to customize the way a web page displays or behaves, by using small bits of JavaScript.
You can write your own scripts, too. Check out http://wiki.greasespot.net/ to get started. Many scripts already exist, probably ones to enhance your favorite sites. Find them at http://wiki.greasespot.net/User_Script_Hosting .
Having trouble? Please don't post comments here, nobody will see them. If you need help, please read:
http://wiki.greasespot.net/Greasemonkey_Manual:Getting_Help