I cannot access netscape.aol.com myself. I am in the UK and I keep defaulting to the netscape.aol.co.uk web site.
However, on the chance that your bookmark is now ineffective, (may be they have changed the link), are you able to sign in for Netscape mail from that netscape.aol.com home page?
If not, what error messages? If there is a Server Not Found message again it would seem their server is down and you may need to contact them, either by phone, (preferably), or via their "Contact Us" links.
I use Firefox with Google as my
homepage and have been using the same bookmarked netscape.net email
address for 13 years now. For the last few days I have been unable to
access my email as I am told either "Firefox can't find the server
at netscape.aol.com." or "Firefox can't find the server at
my.screenname.aol.com." Occasionally I can get on to the site by
clicking the Try again button but cannot send messages. Any advice on
this problem would be greatly appreciated.