About interstitial ads
Interstitial ads present a full page ad experience at natural transition points such as a page change, an app launch or a game-level load. Interstitials use a close button that removes the ad from the user's experience. Ads are displayed in an iFrame that floats over the web page or app. By default, all of the pages that make up an ad appear at the top-left corner (coordinates 0,0) of the enclosing iFrame, but this can be modified by adding an offset.