1. A method comprising: receiving a search query from a user; identifying search results responsive to the search query; determining a plurality of concepts matching the search query; retrieving the plurality of concepts associated with the search results using a page-concept index; determining related concepts related to the plurality of concepts matching the search query and the plurality of concepts associated with the search results using a concept graph, the concept graph being an automated taxonomy of online information resources, the concept graph comprising information on a plurality of concepts of the online information resources and further comprising relationships among the plurality of concepts; generating a set of concepts, the set of concepts comprising the plurality of concepts matching the search query, the plurality of concepts associated with the search results and the related concepts; clustering the set of concepts into a plurality of grouping of top concepts, wherein each grouping represents a potential user intention of the user; identifying a potential user intention of the user corresponding to each grouping of top concepts, wherein each potential user intention comprises one aspect of the topic that the user could be looking for, when the user enters the search query; matching each potential user intentions of the user to an advertisement; and delivering each advertisement and the search results to the user.