SAN FRANCISCO RESTON, Va. April 24, 2012
Traditional display ad impression measurement and reporting simply verifies the number of ads that were sent by an ad server to a user’s browser. For a variety of reasons, this way of counting impressions does not ensure that the ad ever rendered within a browser. In addition, ads can load below the fold (requiring a user to scroll down), which means that most users will probably never see the ad unless they scroll down. In the worst cases, some ads load within 1×1 pixels and therefore never render as viewable impressions.
*The Making Measurement Make Sense (3MS) defines "in-view" as 50%+ of the pixels of an ad being visible in the browser, and comScore vCE adheres to this definition for its typical definition of "in-view". The Pretarget studies, however, used a more conservative in-view requirement of 75% visibility.
SOURCE comScore, Inc.