Recently we have been witnessing the phenomena of private Web site owners who are willing to dedicate space on their site for advertisements managed by leading Web companies (e.g., Google, Yahoo). In most cases the choice of the advertisements displayed on a certain site is made without taking into account the preferences of the Web site. In this paper, we focus on the design of mechanisms that are beneficial for both the Web site owner, by allowing placement of highly desired ads, and the advertisers, by introducing a dispensation scheme to reduce the prices paid for highly relevant ads. In this paper, we analyze the case of multi-slots offered by a certain Web site, and we offer three strategy-proof mechanisms that differ in their ranking function, allocation rules, and payment schemes. The performance of all the mechanisms are compared and discussed.