Currently, modal dialogs that fire during beforeunload/unload events are used to confuse users into not being able to leave websites (e.g. to tell the user to click on the wrong button for in the browser's beforeunload alert dialog). They also add a layer of complexity to browser shutdown behavior. I can't think of any legitimate use-case for opening a modal dialog when a user is trying to navigate away from a page.
Proposal: Opening a modal dialog during beforeunload/unload should either throw an error or just silently fail. Ojan
