11. A system for estimating advertisement inventory, stored in a non-transitory medium executable by a processor, comprising: a cluster probability vector processor configured to cluster a plurality of viewed pages into a plurality of clusters to generate a plurality of page view probability vectors that includes a page view probability vector for each viewed page, said clustering based on a frequency of search keywords present in the viewed pages; the cluster probability vector processor configured to cluster a plurality of search keywords into the plurality of clusters to generate a plurality of keyword probability vectors that includes a keyword probability vector for each search keyword, the search keywords based on search keywords previously submitted by a plurality of users, and the plurality of view pages including previously viewed pages corresponding to the previously submitted search keywords; clustering the plurality of viewed pages into a plurality of clusters based on a time-decaying weighted frequency of the search keywords and an intensity value of the search keywords, present in the viewed pages; and a cluster total inventory estimation processor configured to estimate a plurality of total inventories that includes an estimated total inventory for each cluster of the plurality of clusters.
11. A system for estimating advertisement inventory, stored in a non-transitory medium executable by a processor, comprising: a cluster probability vector processor configured to cluster a plurality of viewed pages into a plurality of clusters to generate a plurality of page view probability vectors that includes a page view probability vector for each viewed page, said clustering based on a frequency of search keywords present in the viewed pages; the cluster probability vector processor configured to cluster a plurality of search keywords into the plurality of clusters to generate a plurality of keyword probability vectors that includes a keyword probability vector for each search keyword, the search keywords based on search keywords previously submitted by a plurality of users, and the plurality of view pages including previously viewed pages corresponding to the previously submitted search keywords; clustering the plurality of viewed pages into a plurality of clusters based on a time-decaying weighted frequency of the search keywords and an intensity value of the search keywords, present in the viewed pages; and a cluster total inventory estimation processor configured to estimate a plurality of total inventories that includes an estimated total inventory for each cluster of the plurality of clusters. 13. The system of claim 11 , further comprising: a keyword filter configured to limit the plurality of search keywords to at least one of a predetermined maximum number of search keywords or search keywords submitted in a predetermined time period.