1. A method of facilitating off-site targeted Internet advertising with a first computer controlled by a proprietor of a first Internet site, which proprietor has sold, for a first price, placements of an electronic advertisement on other Internet sites, which advertisement is directed to an offering of a third-party advertiser, the method comprising automatically: a. with the first computer, placing a cookie on each of a plurality of visitor computers visiting the first Internet site; b. with the first computer, detecting those user computers of the plurality of visitor computers that have conducted a specific predetermined action on the first Internet site; c. with the first computer, for each of the visitor computers detected as having conducted the specific predetermined action on the first Internet site, storing information, accessible through the cookie on that visitor computer, indicating that the visitor computer has conducted the predetermined specific action; d. later, with the first computer, in conjunction with a second computer controlling ad space on the second Internet site, detecting visitor computers visiting the second Internet site that have the cookie and with the first computer using the information accessible through the cookie to identify those of the visitor computers visiting the second Internet site that have conducted the specific predetermined action on the first Internet site; e. with the first computer, communicating with the second computer to cause the second computer to direct the electronic advertisement to those of the visitor computers that have been identified, as a result of part (d), as having conducted the specific predetermined action on the first Internet site, for display in ad space on the second Internet site by the identified visitor computers; and f. with the first computer, causing a proprietor of the second Internet site to receive revenue, as a result of part (e), in an amount less than the first price, for display of the advertisement; g. wherein the proprietor of the first Internet site retains at least part of the difference between the first price and the revenue received by the proprietor of the second Internet site.