1. A method comprising: selecting a topic from a hierarchy of topics; receiving, from a user, a seed set including one or more seed pages for the topic; receiving a document that is not associated with the topic; using the seed to determine, with a processor, a topic destination score and a topic source score for the document relative to the document, the topic destination score indicating an amount of content in the document relating to the topic and the topic source score indicating reachability of content relating to the topic through the document; receiving a query; and returning the document as a result for the query based at least in part on the topic source score and the topic destination score for the document; wherein returning the document as a result for the query based at least in part on the topic source score and the topic destination score for the document further comprises calculating a topic score according to a weighted average of the topic source score and topic destination score; and returning the document as a result for the query based at least in part on the topic score.