OHOHOHOHOH -raises hand- I know how
!!!!!!!!!!! I'm using Snow Leopard...
I use Safari. Well, you click on the safari icon, and hold it... then you click option>show in finder>then, you click the little gear symbol next to the eye, and then you look at the list, and click "Get Info"> then, under the little color things, there should be a box that says "Open in 32 bit mode" check that... FF only runs on 32 bit mode computers, luckily, Snow leopard gives you the option whether or not you want 64 bit mode, or 32 bit mode. After that, FF should be working... Reply if it doesn't...

I use Safari. Well, you click on the safari icon, and hold it... then you click option>show in finder>then, you click the little gear symbol next to the eye, and then you look at the list, and click "Get Info"> then, under the little color things, there should be a box that says "Open in 32 bit mode" check that... FF only runs on 32 bit mode computers, luckily, Snow leopard gives you the option whether or not you want 64 bit mode, or 32 bit mode. After that, FF should be working... Reply if it doesn't...
King kinda beat me to it. But instead of using the hassle I use Firefox. Each time I clear the settings to make it run faster. That's all I can say on it..