2. The client apparatus according to claim 1 , wherein when instructed to register the shortcut button, the instructions further cause the client apparatus to display a registration screen on the operation screen, receive inputs of the URL, the display language, and a button name which is a name of the shortcut button, add a unique identifier to the shortcut button, and register the URL, the display language, and the button name.
2. The client apparatus according to claim 1 , wherein when instructed to register the shortcut button, the instructions further cause the client apparatus to display a registration screen on the operation screen, receive inputs of the URL, the display language, and a button name which is a name of the shortcut button, add a unique identifier to the shortcut button, and register the URL, the display language, and the button name. 3. The client apparatus according to claim 2 , wherein the instructions further cause the client apparatus to display the shortcut button together with the button name, on the operation screen.