Hi Margaret,
Here's a rundown of your files (from public_html):
cgi-bin/guestbook.pl: This is where you can set up your guestbook options. It has a list of all the other files that are used. If you need info on how to edit this file, please visit
http://scriptarchive.com , the makers of the guestbook.
guestbook.html: This file is generated/modified by user input from guestbook.pl . It is your current entries.
Any editing should be done inside guestbook.pl . It contains the template for how the page is setup when viewed through a browser.
Cheers!