How to make a pop up survey after they close the window?

We’re a group of students doing a research, we made a website on wikispace.com on a subject called Viral Video’s but we’re trying to do something with the website. And our website comes with a survey.

We wanted to make a venster pop up with the link to our survey when they close that window. I wanted to know how can we make something like that?

A pop up venster to redirect to another link when they close that window.