Sorry, should have been more clear: it seems to me that people are being more vocal about this, than they were Iron Man 3. Maybe there were people who didn't like Iron Man 3, but this seems like it's getting more attention, for some reason.
Why do people have a problem with this, while being perfectly fine with Iron Man 3's post credit scene? That was more of a waste of time; at least this confirmed that some characters were alive (like the Collector and Cosmo), and it revealed Howard. No, it wasn’t a good reveal, but it’s still better than Tony having a sit-down with Bruce Banner for no reason.
@jedixman: @xwraith: more info would be needed to figure what the cause was most likely: a link to which CV page(s) it happened on, as precise a time as possible with time zone, if there was a physical ad on CV that opened it then a screenshot of the ad and it's placement on the site would probably be the most helpful.
The time appears random. It has happened to me in the afternoon, evening, morning, etc. I'll try to pay attention to ads.
I think it's happening the most when I'm on the Off Topic board, in the board or in the main page. Looking at my history, the page I visited was a thread in OT (link) and the main page. I'm not sure which one I was on when it popped up; I might have been in the middle of clicking on the thread. Actually, it's possible that the act of clicking on anything on the site causes the issue, but I can't confirm this.