Starting in 2014, ICAAN (the guys apparently in charge of domain names on the internet) is clamping down on domain name rules. You must verify your ownership of a domain, or they will disable your website.
After 15 days your DNS will be disabled and replaced with a placeholder page that explains what’s going on and how to verify the email address. This means *ALL* domains that are registered with that contact will be disabled 15 days after the verification email is sent until you verify the email address.
On the surface, this is probably a pretty good idea, as it will discourage hackers from creating temporary websites and abandoning them. But in reality, most site owners do not necessarily know who their registrar is, and should they get an email from the registrar, will probably ignore it, since a typical message looks very much like spam.
So, be on the alert for an email from your registrar, and answer it! (Likewise, be careful that you don’t respond to a phishing scam…) Check out this link about how to tell what’s a legitimate message.