[Laminar]

Here's what it eventually forwards to

I don't think I clicked on something that expanded the ad as it was expanded when the page loaded, but I'm sure it's possible.

[Thorzdad]

You probably just rolled-over the collapsed ad with your cursor. I hate those.

[Laminar]

Did it again. Switched to the tab with the ad, and on moving my mouse down to the page content, the rollover triggered the ad to pop out.

[The Final Dakar]

I swear the gorilla one has done similar things to me.

[Laminar]

When the ad first loads, there's a "roll over to find out" button. The "roll over" button disappears after a couple seconds, so if you go back to find out why it popped out, nothing is there.

[reader50]

It's been reported to higher authorities.

[The Final Dakar]

It's in keyboard cat's paws now.

[Oisín]

Originally Posted by The Final Dakar 

I swear the gorilla one has done similar things to me.

Yup, here too. It was maximised when the page loaded. I hadn’t touched my mouse. Only on the first visit after turning on the machine tonight, though—since then, it’s been on its ‘best’ behaviour (i.e., only expands if I roll over it).