There's on particularly malicious pop-up advert that the site is getting paid for - you really have to watch your advertising more carefully!!!
It's trying to download some software to the users machine, and if you say 'no' it keeps on insisting. Takes about 7 or 8 clicks for this to go away, and is the most irritating ad I've ever come across. Of course, now I'm trying to get more details on it, it won't come back... perhaps someone else can give details on this so that you can contact your advertising people and give them a good ***********