19. The method of claim 18 wherein the one or more representative keywords are used to select and serve the at least one advertisement.
18. A method comprising: selecting, by at least one computing device and in response to a request to select at least one advertisement, one or more keyword candidates from an initial web page, each advertisement of the at least one advertisement comprising content that is to be served for display with the initial web page; querying, by the at least one computing device, a network using the one or more keyword candidates to return web pages that include the one or more keyword candidates; identifying, by the at least one computing device, a contextual relevancy of each of the one or more keyword candidates to the initial web page by analyzing the web pages returned by querying the networking using the one or more keyword candidates; and selecting, by the at least one computing device, from the one or more keyword candidates at least one representative keyword for use in selecting the at least one advertisement, the at least one representative keyword being selected using the contextual relevancy of each of the one or more keyword candidates to the initial web page, the at least one advertisement being selected using the at least one representative keyword selected using the contextual relevancy of each of the one or more keyword candidates to the initial page.