Error: Can't open entries file for writing. Please CHMOD entries file to 666 (rw-rw-rw-)!

When trying to post a comment, GBook shows one of these two error messages:

Error: Can't open entries file for writing. Please CHMOD entries file to 666 (rw-rw-rw-)!

Error: Couldn't open temporary file for writing! Please CHMOD the apptmp folder to 777 (rwxrwxrwx)!

This happens because PHP doesn't have write permissions for required files and/or folder.

• On Linux servers:
  
  
• CHMOD these files to 666 (rw-rw-rw-):
  - entries.txt
  - banned_ip.txt
  
  
• CHMOD this folder to 777 (rwxrwxrwx):
  - /apptmp
  
  Tip: learn how to CHMOD here: CHMOD Tutorial.

• On Windows IIS servers:
  
  
• give Internet Guest Account (IUSR) permission to modify, write and read these files and folders:
  - entries.txt
  - banned_ip.txt
  - /apptmp
  
  Tip: you may need to contact your hosting company to set the correct permissions.