16. A non-transitory computer-readable medium storing software comprising instructions executable by one or more computers which, upon such execution, cause the one or more computers to perform operations comprising: receiving, by a search engine and from a classifier, information indicating that, based at least on information about a user that was provided by the search engine to the classifier, the user is likely interested in a set of one or more topics; receiving, by the search engine, a search query with one or more terms that correspond to a subset of the topics in which the user is likely interested; identifying, by the search engine, the subset of topics in which the user is likely interested that correspond to one or more terms in the search query; generating, by the search engine, a search results page that includes a link (i) to a particular resource that the search engine identifies as responsive to the search query, and (ii) that is encoded with topic information for the subset of topics that were indicated to the search engine by the classifier as topics in which the user is likely interested and identified by the search engine as topics that correspond to one or more terms in the search query; and providing the search results page for display.
19. The medium of claim 16 , the operations comprising: determining, based on an indication from an entity associated with the particular resource, whether the entity utilizes information that references subsets of topics indicated as topics in which the user is likely interested; and providing information references subsets of topics indicated as topics in which the user is likely interested based on determining that the entity utilizes information that references subsets of topics indicated as topics in which the user is likely interested.