To provide a method and system for authenticating each home page.

This home page authenticating device is composed of plural clients 2 and servers 1, that conduct data transmission reception on the internet by a predetermined protocol, and a database 3 which serves a public key certificate to each client in addition to the servers. In the authentication of the home page of a server 1 by a client 2, the server 1 down-loads a file including a public key certificate of a home page author and a signature by a private key corresponding to the public key certificate to specific information of the home page to the client 2, a signature certificate program running on the client is started on the opportunity of the download, the certifying processing of the public key certificate is conducted by using the public key certificate of the authentication agency signing on the public key certificate read from the database, and the signature is certificated by using the public key certificate authenticated by the authentication processing.