if i'm playing music and playing a game on my browser at the same time, how do i mute the volume of the browser and keep iTunes volume up. in windows this is fairly easy, is there some program that does this?
I'm surprised no one else remembered Detour from Rogue Amoeba.
It allows you to route audio from specific applications to different outputs and at different volumes. If you wished, you could entirely mute Safari while keeping iTunes at its default level. The program would also allow you to route only iTunes audio to external speakers/headphones and at a different volume.
And it's free
(BTW, the reasons it's now free are outlined here. Basically, it doesn't really work with newer versions of Mail and iChat, however from what I read Safari and iTunes should both function normally. But if you're having some weird inexplicable problem, look there for the reasons it might not be working.)