To add a guestbook to a page, tick the guestbook option on the edit page page.
If you untick this box, the guestbook will be preserved, ie if you later tick the box the guestbook will reappear with the previous entries intact. This may be useful if you want to take the guestbook offline for a while.
If you delete the guestbook, all the entries will be lost, and the guestbook option will be unticked. You can delete a guestbook whether or not it is visible.
The merge guestbook option converts the guestbook entries into editable text in formatted text format. This can be useful if, for example, you have used a guestbook for a discussion and want to summarise what was said.