Edit File: cperror.conf
# Enable SSI handling of error document files <Directory /var/www/html> Options +Includes AddType text/html .shtml AddOutputFilter INCLUDES .shtml </Directory> Alias /cpanel-error-pages /var/www/html/ ErrorDocument 400 /cpanel-error-pages/400.shtml ErrorDocument 401 /cpanel-error-pages/401.shtml ErrorDocument 403 /cpanel-error-pages/403.shtml ErrorDocument 404 /cpanel-error-pages/404.shtml ErrorDocument 413 /cpanel-error-pages/413.shtml ErrorDocument 500 /cpanel-error-pages/500.shtml