Contextual advertising is a form of targeted advertising for advertisements appearing on websites or other media, such as content displayed in mobile browsers. The advertisements themselves are selected and served by automated systems based on the content displayed to the user.
Contextual advertising is targeted to the specific individual visiting a website (or page within a website). A contextual advertising system scans the text of a website for keywords and returns advertisements to the webpage based on what the user is viewing. The advertisements may be displayed on the webpage or as pop-up ads. For example, if the user is viewing a website pertaining to sports and that website uses contextual advertising, the user may see advertisements for sports-related companies, such as memorabilia dealers or ticket sellers. Contextual advertising is also used by search engines to display advertisements on their search results pages based on the keywords in the user's query.
Google AdSense was the first major contextual advertising program. It works by providing webmasters with JavaScript code that, when inserted into webpages, displays relevant advertisements from the Google inventory of advertisers. The relevance is calculated by a separate Google bot, Mediabot, that indexes the content of a webpage.
Since the advent of AdSense, Yahoo! Publisher Network, Microsoft adCenter, and others have been gearing up to make similar offerings.
