jQuery - Alert on Browser's close button click

Hello
I need to find browser close button click event in my web application. I need to show some alert message on that event. I tried to do it using window.onbeforeunload event, but it gets called on every page navigation or page refresh
I need to execute that function only on close button click event

Hi,

don't do it. When you annoy your users with stupid alert messages blocking their whole browser window, you'll prevent nobody from leaving your site, but many will never want to come back.

I think it depends on which browser the client is using. I use this for one of my sites...