Downnotifier is a great website to get a free notification
when one’s site is offline. This checks sites number of times per day. You will
get unlimited email and SMS notifications and that will do the best to tell you
why your site was down by providing the HTML status error code, when possible. Your clients can log in any time to manage
their sites through an interface branded with your logo and company color. Email
notifications sent from the domain (or your own, with Custom Plans) alert you
and your clients when their sites go down and when they come back up.
