Interstitial advertising is one of the ads that shows your site in full screen and these are important tips for ad registration.
Is your site showing error-free Interstitial ads?
To know the answer to this question, please refer to the following link.
After you have entered the link, enter the URL of your site such as the image and click on the Generate Iframe button. If your site image is shown in the box to the right, your site is eligible for Interstitial ads. The image below shows the site is not suitable for Interstitial advertising.
This error is related to the script scripting type.
You can create a subdomain to fix this problem
This will increase both the site visitors and your ads.
And your interstitial ad will look like this