Ad stacking - "parent-url-15"
Fraudulent sites increase the number of ads they show per page by stacking ads on top of each other in the same ad slot
There’s been enormous evidence over the years of this practice by shady, unscrupulous, and outright fraudulent sites.
In FouAnalytics look in the ancestorOrigins data grid to see if this is happening in your campaigns. If there is more than one entry in each row and the left-most entry is not an ad serving domain, then it is stacked iframes or nested iframes. You may see double stacking or triple stacking. In some extreme cases, there’s more! Here’s an example of 15 (parent-url-15 means this is the 15th url in the stack)
In addition to just sticking more ads on top of each other to inflate ad revenues, the chart below show examples (yellow highlight) of pages loaded by other sites. IN my experimental campaign I see my ad is loaded on drudgereport.com (right-most entry in ancestorOrigins) and drudgereport was loaded by a handful of other sites. This is a common technique to inflate traffic (load entire webpages in hidden windows).
In case you don’t want to look through all the raw data yourself, there’s a short cut. Use the Domain App report tab and scroll down to the Stacked Ads section. Each row lists the domain in question, the % column shows the percentage of that domain’s impressions that have this characteristic. This is a list of sites you should consider adding to your block lists or removing from your include list to progressively clean your campaigns.