Um, FF. I wasn't even aware that AIM (AOL Instant Messenger) had it's own web broswer.
That said, if you're using a Mac, there are a ton of great browsers to experiment with and to choose from. The stock OS X Safari, FireFox, by the same makers of FF there is the Mac-looking Camino. There's Shiira and Opera and I bet others that I've forgotten.
I use sea monkey. Also made by mozilla. Same people who make firefox. It works on MAC, Windows and Even Linux. At least Ubuntu 6.06 DD did while I had it.