ResolutionMost probably some error occurred during the page processing. If you accessed PHP page, to see the error description you have to enable error reporting in /etc/php.ini and restart apache. Edit php.ini and set:
display_errors = On
Now you should see the real error. If it is still not clear, examine Apache log files. The domain's log files are placed in $HTTPD_VHOSTS_D/domain_name/statistics/logs/ directory, and main Apache logs are usually located in /var/log/httpd/ or /var/log/apache2 depending on the OS that is installed on the server.