Proof of performance
Some advertisers may want proof that the ads they've bought have actually run and that click-through figures are accurate. In print media, tear sheets taken from a publication prove that an ad was run. On the web, there are technologies such as DART that are widely accepted as proof of performance. Some buyers rely on the integrity of the media broker and the website. The ad buyer usually checks the website to determine the ads are actually running. Most buyers require weekly figures during a campaign. A few want to look directly at the figures, viewing the ad server or web site-reporting tool.