27. A system comprising: one or more computers; and a computer-readable medium coupled to the one or more computers having instructions stored thereon which, when executed by the one or more computers, causes the one or more computers to perform operations comprising; receiving a request to perform a search at a general search engine site, the request comprising a query received from a user through a search query interface presented on a third party website; accessing a search customization profile defined for the third party website by a provider of the third party website, wherein the search customization profile includes a topic identifier; mapping the topic identifier to a specific topic to be used for customizing the search; retrieving a set of documents responsive to the query, each document in the set of documents having an information retrieval score; adjusting the information retrieval score of each of the documents that are associated with the specific topic by a weight value associated with the specific topic; ranking the set of documents according to the respective information retrieval scores after adjusting the information retrieval score of each of the documents that area associated with the specific topic; and returning to the third party website, in response to the request, search results identifying at least a highest ranking portion of the set of documents and the rank order of the documents in the highest ranking portion.
34. The system of claim 27 , wherein the operations further comprise: receiving a weight by which the each of the set of documents can be ranked by the search customization profile.