This is the situation: I've been browsing the web for an hour in pursuit of some bit of technical information and have visited several dozen websites that I don't even remember anymore. I've finally found what I need so I start closing the web browser, only to discover that — aaargh! — there's a popup ad hiding underneath!

My blood boils. What insidious website is responsible for this circumvention of my browser's popup blocker? I want to make it pay for its crime. I'll write angry emails. Leave bad reviews. Even block it from my Google search results — yes, that'll show it!

But I've reached an impediment. The offending site has already been closed.

Is it too late to deduce the advertisement's origin? Or can I somehow un-pop the popup?

Here's a test page. With only the popup left on your screen, can you deduce that it was caused by visiting PasteHTML?