A present server transmits to a second user terminal attribute information authentication request information for requesting authentication of attribute information registered by a first user when a predetermined request is received from a first user terminal. Also, the server registers authenticated information in association with the attribute information of the first user when the authentication information, which indicates that the attribute information registered by the first user has been authenticated, has been received. When a request is made to view the attribute information of the first user, the existence of the authenticated information is determined, and if the authenticated information is registered, attribute authentication display information is generated and transmitted so as to be visually and identifiably displayed on the user terminal to indicate that authenticated information exists.