Recently, the World Wide Web (WWW) has been attracting much attention as the predominant method of sharing information using multimedia contents. However, when users want to provide multimedia contents on the Web, they must learn how to use authoring software or how to write HTML documents. In this paper, we propose a Web information-sharing system called "Big Blackboard," which is based on a large Web page. The large Web page can act as a metaphor for real-world bulletin boards to realize not only a one-dimensional message board but also a two-dimensional message board on the Web. Any user can easily provide multimedia contents using unlimited layout through a Web browser without needing to know HTML. In the case of displaying on a large Web page, loading Web page contents onto a Web browser may require users to wait a long time. We propose a novel method that reduces transmission cost by only loading the contents within the scope at which a user is looking at an entire Web page. The experimental results demonstrate that our method can effectively reduce user waiting time for loading a Web page.