10. A system comprising: one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising: receiving a submission of a first resource locator for a first alternative search result by a first user using a first user device, wherein the submission by the first user comprises a user selection by the first user of a first subpopulation of users, among a plurality of subpopulations of users of a search engine, to receive the first alternative search result in addition to search results generated by the search engine for a first query; associating the first query with the first alternative search result and the first subpopulation of users selected by the first user; receiving a second query submitted from a second user device by a second user different from the first user; obtaining, from the search engine, second search results responsive to the second query; determining that the first query matches the second query and that the second user is a member of the first subpopulation of users selected by the first user to receive the first alternative search result in addition to search results generated by the search engine for the first query; in response to the determining, generating a search results page that includes the first alternative search result in addition to one or more of the second search results; and providing the search results page to the second user device for presentation to the second user.
11. The system of claim 10 , wherein the search results page provides an identifier of the first user with the first alternative search result submitted by the first user.