A feature available for supporters where you can leave a short message on the clubpage visible for everybody, opposed to the private HT mail. Along with HT mail and press announcements it helps build the community.
Guestbooks can only be signed by supporters but the content of every guestbook is available for every user to see.
A guestbook message can contain up to 300 characters, though you may sometimes experience a minor counter bug.
Hattrick Clubhouse also offers a guestbook feature.
The signing of numerous guestbooks by copy-pasting the same message is considered to be spam.