A guestbook? Honestly? Really?
Classic mate! I started making websites when I was 13/14, which could be however long ago, until I tell you the year .. 2003. Early days on the web (ok that's not terribly true) and obviously I went for Geocities :) Classic. The Guestbook was a main feature! It's pretty basic and all, but was the solo form of interaction/feedback back then and this site doesn't really have anything else.
It's just lovely and nostalgic for me XD If you're reading this then you might as well go ahead and leave something!