To add a message or to reply to an existing message, you have to be a member of this site, and to be logged on. That may sound like a constraint, but that's not that much and it's very easy.
Being a Member
Being a member of this site doesn't require anything from you. Your personal information won't be given to anybody, and won't be used for anything else than giving you access to this site. On the other hand, being a member allows you to add new messages or to reply to existing messages. That also allows you to see the dates in your local time instead of seeing them in server's time zone, and to see flags that indicate new and modified messages.
However, being a member doesn't allow you to post everything, and I reserve the right to remove any message that I'd find incorrect.
To become a member, just go to the Sign Up page, and enter your name, your email address, and the password of your choice (write it down somewhere). Click on "Signup", that's it.
Maybe don't you want to reveal publicly your email address? That's perfectly your right, and of course that's possible. When you're a member of this site, go to the page members/settings/preferences and check the radio button that reads "keep my email address private". Once you've clicked on "Save Changes" your email address will be replaced everywhere with a dummy address, including in the messages you've already posted (but you'll still have to use your real address to log on).
When you're a member of this site, you still have to log on to be able to post. To do so, go to the Logon page. Enter your (real) email address and your password. A cookie will be sent to your machine.
If you're not the only one to use this machine, you should log off when you're done, to prevent someone else to post in your name. Just go to the Logoff page and click on the logoff button. That's it.
Click on "New Message" in the left side column. You'll get a form where you can enter the subject of your message and its body. When you're done, click on "Submit Changes". You'll be able to edit or delete this message.
Your new message will appear on the Guestbook's homepage within a few hours.
Editing a Message
You can edit only the messages that you wrote. Find the message to edit, and click on "Edit". When you're done, click on "Submit Changes".
Deleting a Message
You can delete only the messages that you wrote. Find the message to delete, click on "Edit" and then click on "Delete Page".
The messages whose sender is Webmaster and whose subject reads "Message de/by ..." where originally posted on the previous version of this site. New messages won't appear to have been sent by the webmaster.