Any content provider, such as a Website that generates pageviews, with available ad spots can sell such ad spots with fine granularity such as on a per pageview basis, or even on a per ad spot basis. One or more ad spots can be sold for the highest compensation for that pageview. These sales, such as via arbitrated offers, may be dynamic, because many pageviews are not determined until a user request is received, and because the winning ad provider(s) for a pageview might not selected until the page request is known. This may be done by (a) accepting ad spot availability information from a first party, (b) multicasting ad spot requests for offers using the accepted ad spot availability information to at least two second parties, (c) receiving offers, (d) determining at least one winning ad using the offers, and (e) providing information concerning at least one of the at least one winning ad to the first party. The compensation can be made fairer for the Website owner, even in cases where there is an information disparity. This may be done by using a dominant bidding strategy. Alternatively, or in addition, this may be done by having the party with the information advantage, which will normally be the ad network, make a priori guarantees with respect to compensation.