#viewability is a huge issue: 56.1% of ads served on Google were never seen as they were outside the browser window http://t.co/74fn2mTgLE
Google Just Admitted More Than Half Of The Ads It Serves Are Never Seen
Online ad viewability is a hot topic in advertising right now, as marketers are becoming more aware (and concerned) that many of the ads they buy online are never actually seen by people. Advertisers are also shifting to pay only for ads that have actually been viewed, as opposed to those that are just being blindly served.
http://uk.businessinsider.com/google-display-ad-viewability-study-2014-12?r=US#ixzz3KvHRMDre