Some tracking systems track a view or “impression” when an ad is requested from the ad server. This means advertisers can actually pay for ads that don’t fully render on a web page (viewers frequently go to another web page before ads load.) On top of that, if the ad does render, but placed outside the viewable area of the browser and the viewer does not scroll down to see it, advertisers again pay for ads that cannot be viewed!

This technology has redefined online advertising and brought benefit to both advertisers and web publishers:

Advertisers
No longer pay for "views" that are not viewed.

Web Publishers
Fairly monetize all of your web page space. Place CityAds Billboards anywhere. If the viewer can see it, you get credits.

CityAds.net: The most fair and accurate advertising tracking on the web.