Policy abuse
Ad stacking and hidden ads
Feed units are loaded where nobody can see them, or piled on top of each other, so requests and clicks are counted without any real viewer.
How it works
Ad stacking places several ad units in the same spot like a stack of paper; only the top one is visible but all are counted. Hidden ads are loaded in a frame one pixel wide, off the edge of the screen, or behind other content. On a search feed, the equivalent is loading results pages or related-search units invisibly, or more of them than the feed permits.
A unit nobody can see can still be "clicked" by a script or by a misplaced tap on whatever sits above it. Yahoo's partner rules, for example, prohibit pages with no content and require accurate placement information in every ad call, because the feed needs to know what the user could actually see.
Who pays for it
Advertisers, charged for clicks from invisible placements. The feed provider, when the search engine audits the implementation.
Who does it, and why
Publishers and app developers padding request and click counts without adding audience.
Warning signs
- More ad requests per page view than the visible layout can explain.
- Feed units reported at tiny or zero dimensions.
- Clicks recorded on units that were never in view.
- Pages that look empty to a visitor but generate feed activity.
Defences
- Audit partner pages in a real browser and count visible units against requests.
- Use the feed's standard code unmodified, with the permitted number of blocks.
- Measure whether each unit was in view before the click.
- Require partners to declare page layouts and notify changes.
An example
Illustrative: a page shows one visible related-search block but loads four more in hidden frames. For 1,000 visitors the feed logs 5,000 requests. Coverage and click rate per request look oddly low on four-fifths of them, and the mismatch between 1,000 page views and 5,000 requests is exactly what an implementation audit checks first.