I have a Late 2007 MacBook 2.2 Ghz. Still a great machine, especially for its age. One thing I've noticed recently is that when I'm running Firefox, even if I just have Firefox and nothing else open, the fan will rev up to max speed and the CPU's temperature will go through the roof - I've even seen it hit 100 degrees celsius a couple of times. This is just with Gmail, Facebook, and a forum open. In comparison, if I use Safari the CPU sits on around 55 or so degrees, and the fan hums along at 1800 rpm.
I've tried clearing everything from my history, just wondering if anyone has any other ideas? Or if this is something that Firefox just does.