Advertisement generator based on external traffic

An external traffic advertisement system is provided that generates advertisement sets based on analysis of visits to a web site that were referred by an external source. The advertisement system aggregates the referral information for each referral type. A referral type may be defined by one or more of keyword text derived from the query text of the referrals, landing page type, external source, product identifier, and so on. The advertisement system may, for each referral type, aggregate the total revenue from the visits of that referral type and may generate a count of the number of converting visits for that referral type. The advertisement system then identifies those referral types whose aggregated information satisfies an advertisement criterion and generates an advertisement set for each identified referral type with a keyword derived from keyword text and with a link based on the landing page type of the referral type.