Javascript: how to overwrite page reload event?

What I mean is - when user clicks on some browser page reload/refresh button we do not want to reload page - we want to capture that event and call some function (for simple example one with some alert). I need开发者_高级运维 it to work in IE6 and up and Chrome and Firefox3+ of course. How to do such thing (not using jQuery and other libs)?

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It's not possible.

You can detect when an unload occurs, but you can't detect what caused the unload and you can't cancel it without the user's consent. For instance, typing a new address in the address box, clicking a link, submitting a form, selecting a bookmark or refreshing the page will all fire an onbeforeunload event.

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You cannot. You can't change the operating system functionality from within any browser except IE.