1. A computer-implemented method of processing Web activity data, comprising: obtaining a collection of Web activity data generated by a plurality of users at a plurality of Webpages associated with a plurality of unaffiliated Websites, wherein the Web activity data comprises a plurality of query Uniform Resource Locators (URLs) that represent searches performed by users; extracting a plurality of search terms from the plurality of query URLs and associating each of the plurality of search terms with a corresponding Webpage, wherein extracting the plurality of search terms comprises extracting a target class of information from a URL query field that has been identified by a classifier generated by a training system; and generating statistical data from the Web activity data based, at least in part, on the search terms, wherein the statistical data comprises a first statistical data for a target search term associated with a target Webpage and a second statistical data for the target search term associated with another Webpage.
1. A computer-implemented method of processing Web activity data, comprising: obtaining a collection of Web activity data generated by a plurality of users at a plurality of Webpages associated with a plurality of unaffiliated Websites, wherein the Web activity data comprises a plurality of query Uniform Resource Locators (URLs) that represent searches performed by users; extracting a plurality of search terms from the plurality of query URLs and associating each of the plurality of search terms with a corresponding Webpage, wherein extracting the plurality of search terms comprises extracting a target class of information from a URL query field that has been identified by a classifier generated by a training system; and generating statistical data from the Web activity data based, at least in part, on the search terms, wherein the statistical data comprises a first statistical data for a target search term associated with a target Webpage and a second statistical data for the target search term associated with another Webpage. 3. The computer implemented method of claim 1 , wherein generating the statistical data comprises maintaining a set of counters, each counter corresponding to the target search term and one of the Webpages in the Web activity data, and each counter tracks the number of times that the corresponding target search term occurs at the corresponding Webpage.