I just figured that the people running the forum might be interested to know:
if you visit the forum from a different country (in my case Brazil) the pop-ups for advertisement are so aggressive they take over the full screen.
I tried under Safari, Firefox and Iron and always had the behavior that the advertisement expanded to the full screen (famerama advertisement).
Thus even seeing the forum was impossible. Backward navigation led to the page before the forum.
So, simply not usable. I had no problems visiting recently from the US though.
I am now using a proxy in Germany (probably leads to different advertisements), no problem either...