I know the session restore is a very useful feature. And a lot of people actually rely on it. But I find a bit annoying that it has to prompt me every time I start firefox.
I read somewhere that it is actually a bug in that firefox cannot distinguish between a machine shutdown and a crash. It thinks it crashed, an so prompts you if you want to continue off with the previously open windows that you had.
Anyway, until they get this fixed, I'm turning it off. Here's how to do it:
1) Open firefox and type the following in your address bar:
2) Right-click, and select:
New -> Boolean
3) In the dialog box, type the line below and press ok.
4) Set the value to:
You're done. Enjoy!