AdWords~Site targeted advertisements

In 2003 Google introduced site-targeted advertising. Using the AdWords control panel, advertisers can enter keywords of interest, and Google offers to place ads on what they claim are relevant sites within their content network. Advertisers then bid on a cost per mille (CPM) basis for placement. However, Google does not provide advertisers with a list of sites where their ads have been placed, and there is evidence that many of the "content network" sites are merely ad pages set up on parked domains. Advertisers can provide a list of sites where they do not wish their ads to appear, but cannot obtain a list of sites where their ads could or do appear.