Nothing to worry about mate.
You may notice that the ad banners are only on threads posted in the "For Sale" section of the site, they are placed there deliberatley as a higher traffic area will generate higher revenue from the ads...
It's been testing for a while and the site is the sole beneficiary from these pay-per-click ads I believe so it's all good
To put your mind at rest, check out foot's first post on his massive "creed and demon spares" thread