You might have seen it happening so many times that 160X600 AdSense ads appear in a 300X600 ad slot. Similarly, 728X90 ad appear into 970X90 ad slot. Why does this happens?
Why do 160X600 Advertisements appear in a 300X600 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. Specially, 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.