Abstract: A method for determining an ad to display in an ad unit is disclosed. A specification of a targeting vendor ad is received from a targeting vendor, wherein the specification includes a targeting vendor commission. A targeting vendor ad value is determined based at least in part on the targeting vendor commission. The ad to display in the ad unit is determined, based on a comparison of the targeting vendor ad with other ads, wherein the comparison depends at least in part on the targeting vendor ad value. A method for determining an ad to display in an ad unit is disclosed. A specification of a targeting vendor ad is received from a targeting vendor, wherein the specification includes an indication of an ad value guaranteed by the targeting vendor. A targeting vendor ad value is determined based at least in part on the indication.