Testing ad block visibility
To provide partners and advertisers with objective statistics, the Yandex Advertising Network counts only impressions of those blocks that were seen by website visitors and app users.
The reasons why website visitors did not see advertisements on the site could be as follows:
The ad is displayed beyond the visible part of the site: for example, when ads are positioned at the end of the page or in a part of the page that is not seen on the screen without scrolling.
The ad code did not display the ad quickly enough before the visitor left the page: for example, when a page contains a large number of elements like pictures, video clips, large tables, etc. This problem can be especially frequent for visitors who have slow internet access.
In this case, you can change the location of the ad code within the page's HTML code (for Direct ad blocks) so that the ad block is loaded before the above-listed elements are called, or you can use the asynchronous ad call code (for Direct and RTB ad blocks) to load pages and the ad code simultaneously.
There could be a conflict between ad code and other scripts running on the page: in this case, you can run a script check and find out which of them is affecting the Yandex ad display. One by one, disable all scripts that run on the page in order to identify the one that is causing the conflict.