9. One or more computer storage media having stored thereon computer-executable instructions that, when executed by a processor, causes the processor to perform operations comprising: identifying candidate phrases in a webpage based at least in part on an online encyclopedia phrases index; associating the candidate phrases with online encyclopedia entries; constructing a semantic bipartite graph between the candidate phrases and categories that include the online encyclopedia entries; and selecting one or more of the candidate phrases as keywords for advertisement targeting based at least in part on quantities of associations between a candidate phrase and the categories of the candidate phrases, the associations being derived from the semantic bipartite graph, in which the keywords for advertisement targeting are extracted by mining semantics provided by an online encyclopedia taxonomy.
13. The one or more computer storage media of claim 9 , wherein the associating includes assigning the candidate phrase to a single online encyclopedia entry.