PINGuana tests your URL once every second and emails you within 90 seconds if the state has changed. This state change can go from live to 404, live to server error, etc. etc. meaning that in most cases, the url goes to a server error - you get notified. When it goes from server error back to live, you get notified again. The system is super simple and perfect if you just want to know whether your home page is up, or down.