The large preview (linked at the top of the page when you are logged in) uses a large screenshot in the background to give an idea of what your site might look like. Simply rollover your screener name here and click the preview button to see this:
This is an easy way for us to show you how your current screener theme might look on top of your page, but it can't be completely accurate because the screener is not actually interacting with your site. You need to take care to test your screener before putting it on a live site. Keep in mind if you see any asterisks, that is only in preview mode when logic is turned on. This is designed to show you which responses will yield a "congrats" page. Lots more info about how logic works here.