Updated to make it way more awesome.

A bug has come to my attention that affects L4D though, turns out that L4D and newer steam games have Steam IDs of the form STEAM_1:X:Y whereas older games have STEAM_0:X:Y. The ones reported by L4D are actually correct but for historical reasons (read: people whining), older games report incorrect IDs. I'll be fixing this soon but just a heads up in case you want to make someone and admin/ban them and it doesn't work - all you need to do is change the first number from 0 to 1.