1. A method comprising: sending, to a client, client software that, when executed on the client, causes the client to: receive real-time search results for a first search query and a time token, wherein the time token is data that identifies a most-recent time that any resource identified by any of the received real-time search results was updated, present the real-time search results for the first search query, re-submit the first search query with the time token, obtain additional real-time search results that are more recent than the most-recent time identified by the time token, wherein an additional real-time search result is more recent than the most-recent time identified by the time token when a resource identified by the additional real-time search result was last updated more recently than the most-recent time identified by the time token, and present the additional real-time search results.
2. The method of claim 1 , further comprising: receiving the first search query from the client; determining that the first search query is a search query for which real-time search results should be returned; and sending to the client a user interface document that contains the client software as a response to the first search query.