Simple PHP Guestbook

FEATURES: - add message form with fields: name, email, message, "private" check and "response required" check"; - message listings with configurable number of messages per page; - administration section where you approve messages, delete or see private messages; - notification sent to owner after each entry submitted. If "private" flag is set, message will not appear online; - show/hide/delete messages from admin section; email validation on submit form: the form is tested for correctness of email address and also if user has entered any text; - HTML code spam protection: no HTML code is allowed inside the messages.