If you try to look up the host name:
You should get an error saying that this host doesn't exist. It can't exist, because that domain name isn't registered, as shown here:
Domain names in the .com and .net domains can now be registered
with many different competing registrars. Go to http://www.internic.net
for detailed information.
No match for "THISDOMAINDOESNOTEXISTANDITSHOULDNOTRESOLVE.COM".
Last update of whois database: Tue, 16 Sep 2003 06:19:27 EDT
Unfortunately, because VeriSign is incompetent, and has decided to try to basically screw over the Internet community by ignoring and breaking Internet protocols, if you try to check the host name I mentioned above, you *will* get a result.
You'll be pointed to one of VeriSign's web servers. In other words, no host name lookups for non-existent domains will every return negative. Instead, you'll always receive the address of VeriSign's web server. This will break a lot of things, and cause a lot of confusion and frustration.