You might have seen it happen so many times that 160×600 AdSense ads appear in a 300×600 ad slot. Similarly, 728×90 ads appear into 970×90 ad slot. Why does this happen?
Why do 160×600 Advertisements appear in a 300×600 Ad Slot?
To help increasing competition for some of larger ad sizes, display of similar sizes can also appear in the ad slot. When this happens, the smaller advertisement is served at the top of the larger ad unit centered horizontally. Especially, for ad units opted into showing, you might occasionally see the following:
- a 160X600 ad in a 300X600 ad unit
- a 728X90 ad in a 970X90 ad unit
- a 300X250 ad in a 336X280 ad unit
So by putting the larger ad sizes on your site, you can create greater competition for the same space creates more competition in the auction. Just like when you opt into both Text and Display ads, having multiple sizes compete for the same space creates more competition in the auction. And more competition means higher winning bids.