how is it blacklisted? I'm able to resolve the domains and access the web servers over IP
He mentioned anti-virus blacklists, so if you are not running an anti-virus program that subscribes to those lists, everything will work as expected with no errors or warning. That's my guess.
That's great man! It depends on your DNS, browser, and OS. Avast Anti-virus flags it, and these security vendors have it as flagged: Fortinet Seclookup CRDF We put in requests to them to have it removed.