That's just a summarize of http://freestyler.ws/style/3501/gmail-cleaner-and-tweaker by Nelson@userstyles, all thanks to him. Simply I just adapted the style for me and the latest versions of Firefox 3 beta 5 and Stylish 0.5.6, otherwise the original one behaves a bit weird. Also some features which I don't need and unnecessary code parts were removed.

What it does so far (26.04.08):
* Adds the right border to the mail table
* Blocks the ads in message view
* Removes "Search the Web" button
* Makes navigation items on the left hoverable