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 search query requesting a search of a collection of custom content resources, wherein resources in the collection of custom content resources are resources exposed to a search engine by a user; obtaining a custom content search result that the search engine has identified in response to the search query using a custom search index generated from the collection of custom content resources; obtaining an indication of relative importance for a custom content resource identified by the custom content search result, the indication of relative importance being an indication of the importance of the custom content resource relative to other resources in the collection of resources and being assigned by the user that exposed the custom content resource to the search engine; determining a score for the custom content search result based on the indication of relative importance for the custom content resource; and ranking the custom content search result with one or more other custom content search results that were identified by the search engine in response to the received query, using the determined score.
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 search query requesting a search of a collection of custom content resources, wherein resources in the collection of custom content resources are resources exposed to a search engine by a user; obtaining a custom content search result that the search engine has identified in response to the search query using a custom search index generated from the collection of custom content resources; obtaining an indication of relative importance for a custom content resource identified by the custom content search result, the indication of relative importance being an indication of the importance of the custom content resource relative to other resources in the collection of resources and being assigned by the user that exposed the custom content resource to the search engine; determining a score for the custom content search result based on the indication of relative importance for the custom content resource; and ranking the custom content search result with one or more other custom content search results that were identified by the search engine in response to the received query, using the determined score. 13. The system of claim 10 , wherein the custom content resource is a resource uploaded to the search engine by the user.