User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:2.0b10pre) Gecko/20110121 Firefox/4.0b10pre Build Identifier: Mozilla/5.0 (X11; Linux x86_64; rv:2.0b10pre) Gecko/20110121 Firefox/4.0b10pre With Bug 592822, the quit dialog was disabled. While I do think this is a good thing, and I hope the dialog/pref/browserGlue pieces will eventually be removed, it now makes the browser's behavior inconsistent. If browser.tabs.warnOnClose is true, then the user is prompted when closing a window. It always irked me that this did not happen when quitting or when closing the last browser window, so the quit dialog served that purpose for me. But now, with the quit dialog disabled, browser.tabs.warnOnClose should behave more consistently and prompt the user. In Bug 592822, the argument was that users can just restore their session. But for the users that have disabled the sessionstore, or use clear history on exit, doing this really isn't an option. So now these users have to re-enable the quit dialog and hope it isn't actually removed. IMHO this is a companion to Bug 590483. Reproducible: Always

dupe of Bug 384907 ?

See Bug 627705.