17. The method of claim 15 wherein the plurality of candidate impressions comprise: a first message with an associated first creative; the first message with an associated second creative; and the first message with an associated third creative; wherein the first, second, and third creatives being different from each other.
15. A method comprising: (A) receiving from a client computer a request for an impression to be displayed in a placement of a web page in the client computer, the request being provided by the client computer as a result of said client computer receiving the web page; (B) receiving a cookie from the client computer, the cookie comprising data including behavioral data indicative of categories of websites previously visited by an end-user on the client computer; and (C) using at least the behavioral data to select a selected impression from a plurality of candidate impressions that may be displayed in the placement of the web page, the selected impression being selected from the plurality of candidate impressions based at least in part on anticipated revenue generation, wherein selecting the selected impression from the plurality of candidate impressions comprises: (c1) if all impressions in the plurality of candidate impressions are in a first learning mode, then randomly selecting the selected impression from the plurality of candidate impressions; and, (c2) if all impressions in the plurality of candidate impressions are in a second learning mode, then selecting a highest revenue generating impression in the plurality of candidate impressions as the selected impression; and, (c3) if all of the impressions in the plurality of candidate impressions are in a third learning mode, then selecting a highest revenue generating impression in the plurality of candidate impressions as the selected impression wherein impressions in the first learning mode comprise impressions that have been served less than a first predetermined threshold number of times, and wherein impressions in the second learning mode comprise impressions that have been served more than said first predetermined number of times and less than a second predetermined threshold number of times, and wherein impressions in the third learning mode comprise impressions that have been served more than a third predetermined threshold number of times, said third predetermined threshold being greater than said second predetermined threshold.