15. 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: determining that, among a set of search results that are each identified as at least potentially relevant by a search engine in response to a search query submitted to the search engine, one or more of the search results are each classified by the search engine as very relevant to the search query; and in response to determining that, among the set of search results that are each identified as at least potentially relevant by the search engine in response to the search query submitted to the search engine, one or more of the search results are each classified by the search engine as very relevant to the search query: providing a search results page that (i) includes a subset of the search results, including the one or more search results that are each classified by the search engine as very relevant to the search query, and one or more search results that are identified as at least potentially relevant by the search engine but that are not each classified by the search engine as very relevant to the search query, and (ii) includes a respective image in association with only those search results of the subset that are each classified by the search engine as very relevant to the search query, and (iii) does not include a respective image in association with those search results of the subset that are not each classified by the search engine as very relevant to the search query.
15. 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: determining that, among a set of search results that are each identified as at least potentially relevant by a search engine in response to a search query submitted to the search engine, one or more of the search results are each classified by the search engine as very relevant to the search query; and in response to determining that, among the set of search results that are each identified as at least potentially relevant by the search engine in response to the search query submitted to the search engine, one or more of the search results are each classified by the search engine as very relevant to the search query: providing a search results page that (i) includes a subset of the search results, including the one or more search results that are each classified by the search engine as very relevant to the search query, and one or more search results that are identified as at least potentially relevant by the search engine but that are not each classified by the search engine as very relevant to the search query, and (ii) includes a respective image in association with only those search results of the subset that are each classified by the search engine as very relevant to the search query, and (iii) does not include a respective image in association with those search results of the subset that are not each classified by the search engine as very relevant to the search query. 16. The system of claim 15 , wherein the operations comprise: classifying a specific search result as very relevant to the search query based on an observed historical click through rate associated with the specific search result, the specific search result being one of the one or more search results that are each classified as very relevant to the search query.