Today it wouldn't work because they now have frame-breaking on m.Facebook.com. But if you'd like to see the general template you can email me at the email in my HN profile.

Basically, you position the iframe element over something that will be clicked (such as an advertisement X button), set its z-index so that it is the topmost element, and set its opacity to 0. You can even test to see when the click has occurred by testing for when a certain element on your page has lost the focus.