Activity Monitor
When Activity Monitor shows a process running over 100%, that means it's running on more than one core at the same time with multithreading. Often with multi-core modern Macs the total CPU usage is over 100%, because 100% just means full utilization of one core.
This is typed on a Mac Mini with SeaMonkey. I've had SeaMonkey lock up on occasion, but really only when I've gone completely out of control and have several dozen tabs open. (Although that's much of the time with me.)
Biting the hand that feeds IT
