Browser
ERR_NAME_NOT_RESOLVED The name could not be resolved
What it means
The browser could not turn the host name into an address. That may mean the name does not exist, or that your resolver did not get a usable answer in time, or that DNS is blocked on your network.
Where you usually see it
Chrome and related browsers when DNS fails. It is close to NXDOMAIN, but it also appears when the resolver itself is unreachable.
What to try first
See whether other sites load. If they do, check the spelling of this name. If they do not, check your network and whether a VPN or a custom DNS setting is pointing at a resolver that is down. On a machine you administer, a later retry after you confirm DNS settings is safer than a pile of registry tips.
When to stop
Changing to a random public DNS server can help if your current resolver is failing, and it can also break access to names that only exist on a private network, such as an office intranet.