A collaboration client's behavior is changed according to context while collaborating on an internet. An HTTP request from a customer-side browser is sent to a web server via an information terminal support server. The web server then sends context in response to the request to the customer-side web browser via the information terminal support server. The information terminal support server then checks the contents of the context, and when it is determined that there is agreement with a predetermined condition, a command is inserted into the context. Context without the command inserted is sent to the customer-side web browser, and context with the command inserted is sent to the agent-side web browser. A client program of the agent-side information terminal then reads the embedded command using an API possessed by a web browser and carries out processing in order to prohibit form submission and form alteration and conceal specific forms or fields in accordance with the contents of this command.