To provide a bulletin board system through a WWW suitable for eliminating any unopened article by promoting a user of unopened bulletin board articles to open the bulletin board articles, by periodically informing the user until the user opens the articles.

When a user logs in by a Web browser, and article data to be opened by the user are present, the browser at the user's side is repeatedly informed, until the number of unopened article data is turned into zero. Especially, the interval of the communication of the presence of the unopened articles is changed, according to the division of the bulletin board of the unopened articles or the number of unopened articles, and the user is repeatedly promoted to open the articles, so that the number of unopened articles can be sharply reduced.