public static function getLastVisitedUrl() {
	    $urls = common_session_SessionManager::getSession()->getUserPropertyValues(TaoOntology::PROPERTY_USER_LAST_EXTENSION);
	    if (!empty($urls)) {
	        $lastUrl = current($urls);
	        return ROOT_URL.$lastUrl;
	    } else {
	        return null;
	    }
	}