Request traffic reports. Measure beyond the clickthrough rate, keeping your objectives in mind. The number of times a web page is successfully retrieved and seen by a reader. Impressions - The number of times an advertiser's ad is loaded on a page for a reader to see. CPM - Cost Per Thousand Impressions.
Many websites bill advertisers for each thousand impressions of their ad.
Rotation - A process that enables advertisers to share a good ad position on a page with other advertisers but still be the only ad visible in the spot. Unlike a fixed-size print page, a website can place any number of ads on a single page, just by making the page deeper and deeper. This is done by Rotation. Rotation can also be used by the same advertiser to show three separate ads. From then on, it identifies the reader when they come back to the site.