this code stopped working, so i made updates. you can find them at Google - Remove Text Ads and Sponsored Links.
I'm a huge fan of this style, but it's fallen behind on a few bug fixes and tweaks, so I've decided to post my version. http://userstyles.org/styles/6209
About Google - improved ad remover on Apr 28 2008
About GMail 2.0 Redesigned - Grays and Blues on Apr 05 2008