11. A computer program product, encoded on one or more non-transitory computer storage media, comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising: receiving a search query; obtaining search results that identify a plurality of respective web pages as being responsive to the search query; computing a respective global ranking score for each of the plurality of web pages, wherein each global ranking score is based at least in part on a measure of relevance of each web page to the search query; computing an onsite ranking score for each of the responsive web pages, wherein each web page is a web page on a corresponding website that includes a plurality of other web pages, wherein the onsite ranking score is computed from onsite data that is controlled by a webmaster or a developer of the website, wherein the onsite ranking score represents an indication of importance of the web page as responsive to the search query relative to all other web pages within the corresponding website; modifying the global ranking score for each responsive web page based on the onsite ranking score for the web page; generating a combined ranking of the plurality of web pages based on the global ranking scores of the web pages including the modified global ranking score for each web page; and providing the combined ranking of the plurality of web pages in response to the search query.
11. A computer program product, encoded on one or more non-transitory computer storage media, comprising instructions that when executed by one or more computers cause the one or more computers to perform operations comprising: receiving a search query; obtaining search results that identify a plurality of respective web pages as being responsive to the search query; computing a respective global ranking score for each of the plurality of web pages, wherein each global ranking score is based at least in part on a measure of relevance of each web page to the search query; computing an onsite ranking score for each of the responsive web pages, wherein each web page is a web page on a corresponding website that includes a plurality of other web pages, wherein the onsite ranking score is computed from onsite data that is controlled by a webmaster or a developer of the website, wherein the onsite ranking score represents an indication of importance of the web page as responsive to the search query relative to all other web pages within the corresponding website; modifying the global ranking score for each responsive web page based on the onsite ranking score for the web page; generating a combined ranking of the plurality of web pages based on the global ranking scores of the web pages including the modified global ranking score for each web page; and providing the combined ranking of the plurality of web pages in response to the search query. 13. The computer program product of claim 11 , wherein the onsite ranking score is further based on a relative placement of the particular webpage within an internal structure of the corresponding website.