Even when the user ID concerned is not held at a coordination destination Web site, the present invention makes access to the coordination destination Web site possible using the user ID of a coordination source Web site. According to a representative embodiment, a coordination source application calls the log-in API of a coordination destination Web server on the basis of information that includes a user ID, and the log-in API records the information that includes the user ID as redirect information, generates a redirect token, and adds the token to the URL of a guidance application in responding to the call. The coordination source application redirects access to the guidance application on the basis of the responded URL, and the guidance application generates, when the redirect information identified by the redirect token included in the URL is recorded, a log-in cookie on the basis of the included user ID, and makes access redirected to a coordination destination application.
