Remove ads from Google search/image/Gmail/grups results.This is a Greasemonkey user script.
To install, you need Greasemonkey:
http://greasemonkey.mozdev.org/Install and then restart Firefox and revisit this script.
Under Tools, there will be a new menu item to "Install User Script".
Accept the default configuration and install.
To uninstall, go to Tools/Manage User Scripts,
select "CustomizeGoogle", and click Uninstall.