Correct $basedir:
Make sure you are using the correct path for your $basedir and don't use your web path as your $basedir and make sure the you added /cgi-bin/ to the end of the $basedir if that is were you put book.cgi if not then add wherever you put book.cgi to your $basedir.
Correct $listfile:
make sure that if you changed the name of kitbook.txt to reflect that change in the $listfile
Change the value to 1:
did you change the value from 0 to 1 in the local($check_referer) = 0; line of book.cgi?
Edited The Fla:
Make sure you edited the file guestbook.fla with the above changes and to upload the edited version to your website and not the one that comes in guestbook.zip
The Right directories:
make sure that the files that you uploaded are in the right directories
because book.cgi needs to be in a directory where cgi scripts are allowed and not just any directory on your server.
Further Instructions:
If after reading this tutorial and rechecking everything you are still having problems you can contact me at foofactor@mail.com and I will try to help you out
Tutorial By: Devine a.k.a. daflash
If you use this tutorial and it works for you then please sign my guestbook at www.devinechaos.f2s.com thanks.