Q:

website security of a domain

There is a website and I want to see if it is secure or not:
When I enter the site with the domain address as 
https://2nate.com/ the browser says that it is secure.
But when I enter the domain address as 
https://www.2nate.com, my browser displays a warning that the site is not secure.
What is the problem and are these domains the same and are they secure or not?

A:

They have a wrong record in the DNS.
The hostname 2nate.com has four IP addresses (2606:4700:30:0:0:0:681c:1163,2606:4700:30:0:0:0:681c:1063, 104.28.17.99 and 104.28.16.99). They all have a valid certificate that has an alternative name for *.2nate.com covering both hostnames, valid until 30 Jun 2019.
The hostname www.2nate.com has the same IPv6 records, but different record for IPv4: A 188.40.184.248. The certificate (and HTTPS connection) on that server is invalid in several ways. Changing the A record would make this hostname work perfectly fine with IPv4, too. 
As a user you should only use the hostname that has a secure connection to the correct site. Their error on the other hostname doesn't affect that connection at all. It would be nice to give them a hint, though.

