Greasemonkey is a firefox addon that helps you to install multi utility scripts and manage them and make those scripts work for you.These scripts have done wonders and is one major plus point of firefox.IE users don't loose hope,Keep reading.First i will be mentioning how to install,run and manage greasemonkey scripts on Firefox.
1.Install Greasemonkey addon.
2.Now you have the liberty to install greasemonkey scripts.You can find a lot of them at Userscripts.org
3.If you want to manage edit or uninstall scripts,just right click on the monkey icon on the bottom right corner of your firefox window and choose your option.
For IE users
IE7Pro Compatibility Script-IE7Pro is a free Internet Explorer add-in that permit creation of User scripts like GreaseMonkey.This one will allow IE fans to enjoy the fullfledged luxury of Greasemonkey.Install IE7Pro Compatibility Script.
Related:10 most useful greasemonkey scripts.