1. A system, including: an interface configured to receive a request from a seller, the request including a product identification; and an advertising module configured to assign to the seller, based on a distance function and the product identification, a matching identification entry included in a set of identification entries, and to identify at least one seller ad associated with the matching identification entry, wherein identification of the at least one seller ad is determined by a distance measured between the matching identification entry and at least one extracted identification entry extracted from a selected content page and included in the set of identification entries.