Verify before page refresh or back - is there a way?

[eluser]Barwick[/eluser]
Question - is there a way to verify (via pop-up or some other method) before a user's back to page refresh or hit the browser back button?

For example, if I'm on a page and I go to hit the 'back' button or do a browser page refresh, before I'm able too I'll need to verify (via a pop-up) that I actually want to leave the page...

Not idea where to start with this. Scripts/code/examples anyone? I realize this might not be a Codeigniter related question. Or maybe it is...

Cheers,
Mike