16. A computing device comprising: one or more processors; memory coupled to the one or more processors; and computer-executable instructions stored on the memory and configured to be operated by the processor to perform operations including: identifying candidate phrases in a webpage based at least on an online encyclopedia phrases index; associating the candidate phrases with 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 categories of the candidate phrases, the categories including the online encyclopedia entries, in which the keywords for advertisement targeting are extracted by mining semantics provided by an online encyclopedia taxonomy.
16. A computing device comprising: one or more processors; memory coupled to the one or more processors; and computer-executable instructions stored on the memory and configured to be operated by the processor to perform operations including: identifying candidate phrases in a webpage based at least on an online encyclopedia phrases index; associating the candidate phrases with 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 categories of the candidate phrases, the categories including the online encyclopedia entries, in which the keywords for advertisement targeting are extracted by mining semantics provided by an online encyclopedia taxonomy. 17. The computing device of claim 16 , wherein the operations further comprise generating the online encyclopedia phrases index from one or more of the following: articles, titles of redirect pages, disambiguation pages, and anchor text.