12. 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: detecting an occurrence of a pre-search trigger, the pre-search trigger corresponding to a user action to gain access to a search interface at a particular time; identifying a user associated with the pre-search trigger; identifying a topic classified as a likely topic of interest for the identified user based on a browsing history of the identified user or a search query history of the identified user; in response to detecting the occurrence of the pre-search trigger, determining a confidence score associated with the topic based on the particular time of the user action, the confidence score indicating a likelihood that the topic is of interest to the identified user at the particular time; determining that the confidence score associated with the topic satisfies a predetermined threshold value; instructing a search engine to execute a search using a search query associated with the particular topic in response to determining that the confidence score associated with the particular topic satisfies the predetermined threshold value; and providing a representation of a resource identified in results received in response to the search.
12. 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: detecting an occurrence of a pre-search trigger, the pre-search trigger corresponding to a user action to gain access to a search interface at a particular time; identifying a user associated with the pre-search trigger; identifying a topic classified as a likely topic of interest for the identified user based on a browsing history of the identified user or a search query history of the identified user; in response to detecting the occurrence of the pre-search trigger, determining a confidence score associated with the topic based on the particular time of the user action, the confidence score indicating a likelihood that the topic is of interest to the identified user at the particular time; determining that the confidence score associated with the topic satisfies a predetermined threshold value; instructing a search engine to execute a search using a search query associated with the particular topic in response to determining that the confidence score associated with the particular topic satisfies the predetermined threshold value; and providing a representation of a resource identified in results received in response to the search. 14. The system of claim 12 , wherein detecting the occurrence of the pre-search trigger comprises receiving a request to provide a resource that provides access to a search interface; and wherein providing the representation of the resource identified in results received in response to the search comprises providing the representation before the user enters a query term using the search interface.