1. A computer system for fetching a web page, comprising: an index for use by a search engine, wherein the index indexes a set of previously crawled web pages; a web crawler for fetching a plurality of web pages to update said index; and a storage device that stores information about a set of queries that have been received by the search engine; wherein said storage device further stores data that indicates which queries in the set of queries are needy queries; wherein said needy queries are queries for which the index does not currently index adequate, relevant content; a crawling policy manager, operably coupled to the web crawler, for implementing a policy for estimating an impact, on said needy queries, of fetching a particular uncrawled web page by comparing terms of said needy queries with at least one of: (a) an anchortext of links, obtained from the previously crawled web pages, that point to the particular uncrawled web page, and (b) a Uniform Resource Locator (URL), obtained from the previously crawled web pages, that points to the particular uncrawled web page; a crawl ordering engine, operably coupled to the crawling policy manager, for ordering web pages to fetch by the web crawler based, at least in part, on the estimated impact, on said needy queries, of crawling the particular uncrawled page.