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?
Ok, to answer my own question…
According to Can firefox restore a secure session after an add-on installation? and the page it links to http://kb.mozillazine.org/Browser.sessionstore.privacy_level there’s a Firefox setting ‘browser.sessionstore.privacy_level’ which determines what FF session restores saves (can be 0, 1 or 2 – see second link).
Until FF4 it was default to store/restore only non-secure sessions (that’s why GMail currently asks you to sign in again – they are using SSL/HTTPS), but in FF4 default setting will be to store ALL sessions – so even secure sessions will be restored by FF.