Also, "crash" and "hang" are different: "crash" is program terminates; "hang" is program stops responding/freezes/locks up.
I've had repeated problems with FireFox "hangs" off-and-on over time, usually resulting in the whole graphical interface (but never the mouse, curiously) hanging, and so no way to logout; my usual solution is to switch to a virtual terminal and kill FireFox - it is not necessary to reboot the machine or even logout: ALT-CTL-F1 to get to a virtual terminal, login as root user, and command: killall firefox-bin . Don't forget to logout root, then ALT-CTL-F7 to return to your open session, with FireFox gone bye-bye and everything else OK. Works for me every time.
Of course, this whole exercise will be repeated ad infinitum
until the real problem is fixed. In my experience, it's almost certainly caused by a faulty add-on (theme, extension, plug-in). No way to be sure except disable/remove them all, then enable one at a time until problem is located and isolated. See also: http://kb.mozillazine.org/Firefox_hangs
Yes, would also help to know your Fedora flavor and FF version, etc.