depends on what it was for, I only use subdomains if it is for clearly defined parts of the site for example a forum etc, if it was for a couple of standard pages on your site there really isnt much point.
Different control panels have different methods for the user to create subdomains for example the old version of Plesk all you did was create a folder called subdomains in your root directory and any folder in that was a subdomain (after an hour) but that is not done in the new version which now is done via the control panel.