1. A method of operating a search system, the method comprising: maintaining a database of search listings searchable by a search engine, each search listing being associated with a search term and a bid amount, the bid amount corresponding to a money amount chargeable a search listing is referred by the search engine; receiving a search request from a searcher; identifying search listings generating a match with the search request; and ordering the identified search listings into a search result list in accordance with values of respective bid amounts for the identified search listings, wherein the values of the respective bid amounts are based on: (a) a bid element amount for impression; (b) a value of a bid element amount for clickthrough, calculated based on the bid element amount and probability of a clickthrough event; and (c) a bid element amount for actions; receiving none, one or more of the following: a retrieval request from the searcher to retrieve information associated with a selected search listing in the search result list, and one or more notifications that the searcher has performed one or more respective actions in connection with the selected search listing; debiting an account of the web site promoter associated with the selected search listing and the respective bid as follows: by the bid element amount for impression, by the bid element amount for clickthrough, provided a clickthrough request was received, and by the bid element amounts for, respectively, one or more actions, provided notifications were received for said one or more actions.