A reader asked how to create a visitor registration. I can only think of 2 thing - a Guestbook and a Shoutbox. There are many sites offering free Guestbooks, but most of them require a script, which is usually remotely-hosted and written in a language such as Perl, PHP, Python or ASP. You should also be aware that this leaves you open to link spam where visitors leave messages for the purpose of leaving a link to their sites.
As mentioned above, this Questbook will be hosted on another site. If you want things to remain on your site, you will have to install a "Shoutbox". More about that later.