12. A computer-implemented method of re-ranking sponsored search results by a search engine in response to a search query, the method comprising: retrieving, by a search engine, one or more organic search results and a plurality of sponsored search results (“search results”), along with their respective rankings, associated with a search query; delivering the search results, by the search engine, to a web graph, wherein the web graph contains a plurality of interlinked web documents each represented by a node (u 1 , u 2 , . . . u n ), and is stored on computer storage coupled with the search engine; retrieving, by the search engine, values of one or more operators based on the relative linking within the web graph between the one or more organic search results, the plurality of sponsored search results, and any of the plurality of web documents; calculating, by the search engine, a clustering score for each sponsored search result based on the one or more operators, wherein the clustering score indicates a degree of linking association between each sponsored search result and the other search results; generating, by the search engine, a new ranking score for each sponsored search result based on their respective clustering scores and rankings; re-ranking, by the search engine, the plurality of sponsored search results based on the new ranking scores of each respective sponsored search result; and storing in memory, by the search engine, the plurality of re-ranked sponsored search results in relation to the search query.
12. A computer-implemented method of re-ranking sponsored search results by a search engine in response to a search query, the method comprising: retrieving, by a search engine, one or more organic search results and a plurality of sponsored search results (“search results”), along with their respective rankings, associated with a search query; delivering the search results, by the search engine, to a web graph, wherein the web graph contains a plurality of interlinked web documents each represented by a node (u 1 , u 2 , . . . u n ), and is stored on computer storage coupled with the search engine; retrieving, by the search engine, values of one or more operators based on the relative linking within the web graph between the one or more organic search results, the plurality of sponsored search results, and any of the plurality of web documents; calculating, by the search engine, a clustering score for each sponsored search result based on the one or more operators, wherein the clustering score indicates a degree of linking association between each sponsored search result and the other search results; generating, by the search engine, a new ranking score for each sponsored search result based on their respective clustering scores and rankings; re-ranking, by the search engine, the plurality of sponsored search results based on the new ranking scores of each respective sponsored search result; and storing in memory, by the search engine, the plurality of re-ranked sponsored search results in relation to the search query. 14. The method of claim 12 , further comprising: calculating a FunctionScore(f,u) between each of a possible pair of nodes within the plurality of sponsored search results (S) and the one or more organic search results (O), and the value of each operator (f), wherein the FunctionScore comprises 
 Σ((f(u,o)×RankWeightOrganic)/(1+log(pos(o))))/|O|, for each o in O+Σ((f(u,s)×RankWeightSponsored)/(1+log(pos(s))))/|S|, for each s in S, wherein RankWeightOrganic and RankWeightSponsored comprise normalizing weights applied to the organic and sponsored search results, respectively, and wherein pos(o) and pos(s) comprise the ranking of each organic and sponsored search result, respectively.