Firefox has a feature to restore session cookies after restart (either after crash or if user has set "restore session" option) and that's causing a lot of problems (for example: Firefox session cookies).
However some sites, most notably Gmail, somehow don't have this problem. After it restores session Firefox won't sign you back in Gmail, you'll have to enter user/pass again. (although, I am not quite sure if Gmail uses session cookies at all)
Is there a way for server application "prevent" browser from restoring session cookies? Or is there some way to know that you are in restored session?