Firefox or Safari preventing sleep?

Don't know whether this goes in the Macbook forum or this Applications one. I think it might be app-specific, so here goes.. My Macbook refuses to let itself go to sleep in the allotted 5 minutes of no-activity. It *seems* like it might be Firefox keeping it awake although I think I may have noticed it while my wife left Safari open as well. No, this isn't with movie-playing stuff running or anything like that.

Anyway, what good is auto-sleep if I have to quit all running apps? If I was going to do that anyway, I could have just as easily shut the lid! Is there a way to tell Leopard "nevermind your CPU activity - if there is no keyboard or mouse activity, PLEASE GO TO SLEEP!!!"

 

Ah, cripes - i don't think it was the browsers keeping my computer from sleeping after all. I prematurely posted that last post (sorry). The only thing using CPU this time was coreaudiod (what is THAT?) at about 3.5% and my macbook refused to fall asleep again. No programs running.