Well known, the Google makes money mostly on context ads, and bigger part of such income are coming from context ads on SERPs. That is simple, ads are selecting on search keywords entered by user. Does anyone known a system, that select ads based on context of pages, which links are shown on SERPs ? I guees this might be the next step in contextual advertising: pages that linked from SERP have (usualy) much more information and this allow to select advertising more percisly, and ads may vary more from one SERP to another, and, with search result clustering technique, it's possible to cluster contextual ads too.