Are you getting an error message like the ones below when trying to post a new message?

• Can't open entries file for writing. Please CHMOD entries file to 666 (rw-rw-rw-)!
   
• Couldn't open temporary file for writing! Please CHMOD the apptmp folder to 777 (rwxrwxrwx)!
   

The reason is GBook doesn't have permission to write to a required file or folder. On Linux servers you need to CHMOD required files (entries.txt and banned_ip.txt) to 666 (rw-rw-rw) and required folders (apptmp) to 777 (rwxrwxrwx).

You can learn how to CHMOD files here: CHMOD Tutorial.

Other servers (Windows for example) don't support the CHMOD command. In that case you will need to contact your hosting company to set the correct file permissions for you.