You must have either a dns cache serving you an IP or a private DNS server giving you an IP for the domain.
Publicly the domain has no IP associated with it. The error you're seeing (I'm assuming in a browser) comes from a webserver giving back an error - so it's at least finding the domain and trying to do something. When I try to go to that domain I just get a can't be found error - which is appropriate if you have nothing on it and no IP associated with it.
Not sure why it's parked, but you might also consider putting your own placeholder there, even if only simple static page or a redirect. More search engine friendly in case you plan to use it in the future.