I noticed last night that I couldn't access their service, and it seemed like the domain was pointed at another site.
This morning I couldn't get there either.
Stan has the answer:
Something in the route tables has been poisoned. I have the same problem (the 'site' is blank ATM, but it had had a NETWORK SOLUTIONS beginner's page earlier this eve)
Until the route tables reset to the correct routes, you can still get there through a proxy. Going direct I get a blank page, but try putting wunderground.com into this proxy page and you're in:
Some people can get in, some can't... just depends on the path between you and wunderground. If you hit the buggered section of the routes, you'll be somewhere else (wherever the route is taking it).
WARNING: DO NOT LOG IN FOR A COUPLE OF DAYS in case the server that's being pointed to starts phishing. Within two or three days from today (15 July 2008) the routes should be back to normal.