Sorry, you cannot access guestbook due to improper installation or uninstallation of PEAR-packages. Please contact your host provider to install PEAR-packages as well as submit below command to your host provider.
pear install -f Net_URL
pear install -f Text_CAPTCHA
pear install -f HTML_QuickForm
pear install -f HTML_Common
pear install -f Image_Text
pear install -f Numbers_Words
pear install -f Text_Figlet