MODx page not found...

Stumble upon modx page not found?
MODx by default, will send an error page if any error found during the loading of the page.
its in modx/core/model/modx.class.php

want to see the actual error?
go to the line declaration of
public function sendError($type = '', $options = array()) {
throw new Exception($errorMessage); //after $errorMessage is defined