When Google is not able to monetize an ad, it does not display an ad. Whether or not Google shows an ad is in line with its ability to convey a focused ad in accordance with the attributes of the user and the viewed page. If no advertiser has bid on these elements, Google makes a decision not to expose an ad. Backup ads for Google AdSense are what will show when Adsense cannot display a monetized ad impression. In this case, you have three alternatives for backup ads:Backup ads are used to monetize ad impressions that your initial ad community Google was not capable of monetize.
In order to do this, you has to be signed up with an alternative ad network. See the ad community feedback below if you aren’t already signed up with a distinct ad network except for Google. Remember, if you are attempting to setup Google AdSense or Ad Exchange to back up one or any other, the ad will not show as it’s towards Google’s terms. If you are looking to monetize 100% of your site visitors and your primary ad community is Adsense or Ad Exchange, it is awfully important that you simply use backup ads from an alternative network. Thank you for offering this advice. I am looking to setup backup ads in my account and I was in a position to do it successfully, though I came to an easy query.