For prescribing a state of a selection operating part having options disposed on an operating page displayed, a type attribute of the selection operating part, a display attribute of displaying or not displaying an operating part corresponding to each option of the selection operating part, and priority setting information indicating modification of setting of an option of the selection operating part, are stored, the modification being carried out while the operating page is displayed. In response to a user's operation, a selected or non-selected state of an operating part of each option, or a display attribute may be changed. When a display attribute of an option is changed, information corresponding to a type of the selection operating part having the option and a selected or non-selected state of the operating part having the option is registered as the priority setting information.