Why did my firefox crash?

First congrats for not using Internet Explorer. Try restarting, and if it still doesnt work run it in Safe Mode from the start menu, then disable a plug-in to see which ones causing the problem. But before that try to reinstall Adobe Flash player.

your profile is probably corrupted. If you're on Windows make a new profile like this First, make sure firefox isn't running in task manager (ctrl+alt+del). If you see "firefox.exe", select it and click on end task. once your sure that its not running, click on start, then click on run. in the box paste this in exactly "%PROGRAMFILES%\Mozilla Firefox\Firefox.exe" -profilemanager and click "ok". you will see a small box pop up which lists your existing profiles. create a new profile by clicking on the "create profile" button. You can give any name to the new profile; dont need to mess with the default folder settings. when the new profile name appears in the list, select it and click on the "start firefox" button. it should start up with the new profile.