To promote exchange demand while improving exchange demander's satisfaction in the case of selling commodities in a home page through the Internet.

A commodity seller sets up a home page for selling commodities in a www server connected to the Internet. A new commodity purchaser accesses the home page, executes customer registration (steps #101 to #105) and executes the registration of a commodity to be newly purchased and the input of satisfaction information (steps #108 to #109). The satisfaction information can be additionally inputted later. A registered demander can receive the presentation of new product information in the home page and receives also the explanation or the like of points improved on the basis of the inputted satisfaction information on an old commodity.