Your DNS, or Domain Name System, is necessary for your users to be able to successfully navigate to your website and use your web services. Without it, users would need to memorize exact IP addresses in order to get from Point A to Point B on the internet. And 99.999% of the users don't bother memorizing these details. Therefore, when your DNS fails, your users will be unable to reach your website or web services using your domain name. Oher important thing to keep in mind: your incoming and outgoing e-mail traffic also stops.