I'm working on a web app that under normal circumstances will be happy with the Session_OnEnd event, but when a user leaves a page by closing the browser by either Alt+F4 or just hitting the "X", I'll need to kill the session.

Now, with the onbeforeunload event, I can handle this quite easily in IE, but in FireFox, it's another matter. For one thing, FireFox seems to empty out its event object on a page unload, so it's very...