trojan

When I clicked on this link [Firefox browser] http://www.jemsite.com/forums/f16/rg655-vs-like-new-rg2550z-series-same-price-152906-8.html#post1451210 I got this AVG pop up.

Just the past couple of days my copy of Avast Antivirus has been detecting a trojan horse when visiting the Jemsite..? Now I highly suspect that there isn't a trojan and this is a false positive but how do I stop it happening? The script is apparently the following...

Since a week i have the problem that firefox often opens new windows with commercials,although my popup blocker is activated. I think it's a kind of virus/adware/trojan or something. Does anybody know the name of this malware ? I need the name to search for a removal tool. Thanks