public static function setLastVisitedUrl($url){
	    if(empty($url)){
	        throw new common_Exception('Cannot register an empty URL for the last visited extension');
	    }
        $success = false;
	    
	    $userUri = common_session_SessionManager::getSession()->getUserUri();
	    if (!empty($userUri)) {
	        $user = new \core_kernel_classes_Resource($userUri);
    	    $user = new core_kernel_classes_Resource($userUri);
    	    if ($user->exists()) {
    	        // user in ontology
    	        
    	        //clean up what's stored
    	        $url = str_replace(ROOT_URL, '', $url);
    	        $success = $user->editPropertyValues(new core_kernel_classes_Property(TaoOntology::PROPERTY_USER_LAST_EXTENSION), $url);
    	    } // else we fail;
	    }
	    return $success;
	}