Google admob errod on return ad

I keep getting this error in my debug when ads are about to be displayed.

07-16 14:35:29.630: INFO/Ads(12137): onFailedToReceiveAd(Ad request suc开发者_开发问答cessful, but no ad returned due to lack of ad inventory.)

What does this mean and how do i fix it?

You can't fix that - just there is no ads in adMob, so you haven't got one.

This essentially means Admob does not have enough ad to fill. This is not an error and you can leave it as it is.

Other answers are correct, there are no ads to fill. However, you can link your AdMob to your AdSense account, which will allow it to fill from there as well.