A vehicle mounted unit 1 has a WWW browser for analyzing and discriminating HTML files obtained from the Internet. The HTML files are provided with a tag for the navigation apparatus (extension tag) in addition to a normal tag. The normal tag includes a descriptive statement which is now widely used on the Internet. The extension tag includes a descriptive statement newly defined for the navigation apparatus, and controls the operation of the vehicle unit 1. The vehicle unit 1 discriminates the normal tag and the extension tag at the time of receiving the HTML file, and in the case of a normal tag, executes normal operation (screen display such as characters), and in the case of an extension tag, executes functions for the navigation apparatus.