Sometimes, a website is not working at your own location alone. And rest other countries, the website is properly functioning. This website, website-down.com, helps you in confirming whether the website is actually down or is just non functional in your area alone.
They use three servers located on different continents (America, Europe, Asia) to confirm if a website is not working. This helps in making sure the website is really down, and not only inaccessible from your location.