A network system comprises: a WWW server 40 for executing a server process; a server 10 for providing a proxy server function; a client 20, which is connected to a communication network 30 for accessing the WWW server 40 and the server 10. The server 10 stores a Web file 11 that includes a proxy server function that can be displayed as a Web page by a Web browser, and that can be read and activated by the Web browser. The client 20 incorporates the Web browser that displays a Web page based on the Web file 11, which is downloaded from the server 10 via the communication network 30. When the Web file 11 is read by the Web browser, the proxy server function of the Web file 11 is initiated.