title: how to determine if user left our site
body: <p>We're tryin to implement some kind of feedback, which I saw in MSDN web-site. More concrete when user first enters to our site, I want to show a pop-up which will ask user to leave comment rite before he would leave our web-site, and depending on user's answer( it would be some kind of confirmation box with Yes and No), I want to open a pop-up with TextBox for user to leave a feedback. I've searched for this in internet, but all of 'em was about handling window.onload event, the problem is we have more than one page, so I won't be able to determine if user requests another page in our web-site or redirects to another web-site. 
  So this is my problem, any suggestions? We're using asp.net.
  Thanx beforehand.</p>