protected function _validUrl($url) {
		$headers = Utility::getHeaderFromUrl($url);
		if ($headers === false) {
			return false;
		}
		$headers = implode("\n", $headers);
		$protocol = mb_strpos($url, 'https://') === 0 ? 'HTTP' : 'HTTP';
		if (!preg_match('#^' . $protocol . '/.*?\s+[(200|301|302)]+\s#i', $headers)) {
			return false;
		}
		if (preg_match('#^' . $protocol . '/.*?\s+[(404|999)]+\s#i', $headers)) {
			return false;
		}
		return true;
	}