@doqck, as I see you do not use AdBlocker, you realize how much money it costs to run a website, you know that Ad Revenue is the only way this site stays up, and you have made several statements stating you do not like the ads. But I very much advise against throwing accusations around and refrain from commenting on the game designers page. They are most likely not the ones responsible, as this pop up appears to be using AGs particular theme.
I won't speak for the mods, admins, or Web designers, but it appears these ads are tied to the completion of certain quests.
If it displeases you to have to deal with ads, either get AG+, or enjoy your free gaming.
There is, however, a possible big bug here, though, it is the issue with closing it, yes?
First, to help address the issue of not being able to close it, and to help whichever admin picks this up:
1) Have you encountered this more than once?
If not, this may be a one off, keep track of when it occurs.
If, so:
2) Have you cleared Cache and Cookies?
3) What browser are you using?
4) Have you encountered this bug on another browser?
Meanwhile, I'll see if I get the same issue, perhaps I can add some input to this.
So, after playing through to the same achievement, I also got a popup ad. I was able to close it, however. May also want to take a look at updating your browser (depending on what you use)
Seeing as it says you've won a 30 day free trial, why not just ask the admin if this is an actual offer? If so, it's a PR freebee, not an ad. If not, report it as potentially malicious adware. That's the right way to deal with these things. Making disparaging accusations, implicit or otherwise, is not.
Sushi Cat-a-pult is one of our games with a special reward system. That (the prize in the screen capture) is a legit reward, and not ad malware or anything like that.