After talking with you right next to me because I had to ask...the behavior you want to see in your guestbook is:
Any user visiting your webpage can leave a comment.
Nice to have a way to encourage or include the user to sign their comment. Perhaps a required separate field that asks the user for how they will sign the comment.
Newer comments on top of older comments.
Include some way of limited the user to one comment per visit.
Hello? Please describe the behavior you want!