3. A method of operating a pay for placement web site, the method comprising: maintaining a database searchable by a search engine, the database including a plurality of search listings, each search listing being associated with an Internet website, a search term and a bid amount, the bid amount corresponding to a money amount chargeable to a web site promoter each time the web site promoter's web site is referred by the search engine, the bid amount including at least one of a bid element amount for impression, a bid element amount for a clickthrough and a bid element amount for an action; at a search engine web server in data communication with the database, providing to a searcher a search list including identified search listings which relate to a request from the searcher; and at the search engine web server, positioning the identified search listings on a web page to be sent to the searcher in accordance with values of respective bid amounts for the identified search listings, the values of the respective bid amounts being calculated based on: bid element amounts for impressions; bid element amounts for clickthroughs; and bid element amounts for actions, wherein the value of a bid element amount for an action is calculated using the bid element amount and a probability associated with the action event, and wherein the probability is calculated using an estimated number of times the action events will occur and an estimated number of times the action events could occur within a specified time period.
4. The method of claim 3 further comprising: at the search engine web server, receiving a search request from the searcher; identifying search listings generating a match with the search request; and returning a search list including the identified search listings on the web page to be sent to the searcher.