This is an Exit Popup

You provoked it when you moved your mouse toward the back button on your browser.

You can put what ever you like in the exit popup, especially an optin form.

If you have not already signed up to our mailing list, please do so here so that I can keep you updated with any new information that can help you with your new landing page system.

See the Stratagem tab inside the editor.

Note:  As of Dec. 1, 2009, Google is not allowing any popups of any kind on their site. Therefore, use the popups in your twitter, facebook and email campaigns.
http://www.google.com/help/nopopupads.html