Yep, CTR is clicks divided by impressions. Although thinking back I believe they were site skins with billboards, not just banners. Even still, for that ad form

Yep, CTR is clicks divided by impressions. Although thinking back I believe they were site skins with billboards, not just banners. Even still, for that ad format on that site I would have expected 1-2%. (And yeah, skins do tend to get more accidental clicks than a small banner ad, but in many cases can also provide better results regardless of accidental clicks.) Depending on the ad format/placement and many other variables, it's possible to have a high-ROI advert with a 0.1% CTR, or a low-ROI advert with 5% CTR (or the exact opposite).