How to do it...

This only works on source engine games but follow the steps to make Alt Tabbing in game, not ♥♥♥♥!

1) Open Library
2) Select a steam source game (CSS, DODS, HL2, GMOD, etc)
3) Right click and left click select launch options...
4) Enter (or add if you already have launch options set), "-noborder" without the "
5) Enjoy alt tabbing without it being a load of bollocks.