14. One or more computer storage media having computer-executable instructions, which when executed perform steps, comprising: determining a bidding keyword vector representing the bidding keyword for an advertisement and a page data vector representing the page data for the advertisement; computing a similarity score for the advertisement based on a vector relationship between the bidding keyword vector and the page data vector; computing a proximity score for the advertisement based at least in part on bigrams in common between the keyword and the page data; combining the similarity score and the proximity score into a relevance score; associating the relevance score with the advertisement; associating relevance scores for a plurality of advertisements; receiving a query; using the relevance scores to rank the plurality of advertisements; and re-ranking the plurality of advertisements based at least in part on a relationship between the query and the bidding keyword and the relevance score of each of the plurality of advertisements.
14. One or more computer storage media having computer-executable instructions, which when executed perform steps, comprising: determining a bidding keyword vector representing the bidding keyword for an advertisement and a page data vector representing the page data for the advertisement; computing a similarity score for the advertisement based on a vector relationship between the bidding keyword vector and the page data vector; computing a proximity score for the advertisement based at least in part on bigrams in common between the keyword and the page data; combining the similarity score and the proximity score into a relevance score; associating the relevance score with the advertisement; associating relevance scores for a plurality of advertisements; receiving a query; using the relevance scores to rank the plurality of advertisements; and re-ranking the plurality of advertisements based at least in part on a relationship between the query and the bidding keyword and the relevance score of each of the plurality of advertisements. 16. The one or more computer storage media of claim 14 wherein determining the page data vector comprises weighing a term in the page data relative to other terms based on page content analysis, HTML attribute analysis, or part of speech analysis, or any combination of page content analysis, HTML attribute analysis, or part of speech analysis.