The domain name could not be translated to an address.
WHAT IT MEANS
DNS failed. The browser could not find out where to connect.
Your hosting and your files are untouched.
THE COMMON CAUSES
The domain has expired Nameservers are wrong or not set The DNS change has not propagated yet The A record is missing Your own device's DNS is failing
CHECKING
Look the domain up in WHOIS. Check the expiry date and the nameservers.
An expired domain produces exactly this symptom, and is the first thing to rule out.
Compare the nameservers against the pair shown for your account in Services > My Services.
IF THE DOMAIN EXPIRED
Open a ticket immediately. Recovery becomes more expensive with time and eventually impossible.
IF NAMESERVERS ARE WRONG
Correct them at the registrar, then wait for propagation.
IF THEY ARE CORRECT AND IT STILL FAILS
Check the A record exists, in whichever system your nameservers point at.
IF IT IS ONLY YOUR DEVICE
Try another network. A local DNS problem resolves itself or is fixed by changing your resolver.