Editing Cost per impression (section)

==Purpose==

Cost per impression, along with [[pay-per-click]] (PPC) and [[cost per order]], is used to assess the cost-effectiveness and profitability of online advertising.<ref name=Marketing_Metrics /> Cost per impression is the closest online advertising strategy to those offered in other media such as television, radio or print, which sell advertising based on estimated viewership, listenership, or readership. CPI provides a comparable measure to contrast internet advertising with other media.

=== Impression versus pageview ===
An '''impression''' is the display of an ad to a user while viewing a web page. A single web page may contain multiple ads.  In such cases, a single '''[[wiktionary:pageview|pageview]]''' would result in one impression for each ad displayed. To count the impressions served as accurately as possible and prevent fraud, an [[ad server]] may exclude certain non-qualifying activities such as page refreshes or other user actions from counting as impressions. When advertising rates are described as CPM or CPI, this is the amount paid for every thousand qualifying impressions served at cost.