Change validations errors messages
http://book.cakephp.org/view/125/data-validation
$validate = array( 'fieldname' => array( 'allowEmpty' => false, 'required' => true, 'rule' => '/^.{6,40}$/', 'message' => 'Your message if rule failed', ) );
List of built-in validation functions: http://api.cakephp.org/class_validation.html