This was an unusual issue today that affected many thousands of sites from a large number of hosting companies that use a server facility (Colo4 in Irving, Texas). They experienced a power outage that literally knocked thousands of sites off-line, including Muppet Central.
The technical details are here for those who are interested...
https://accounts.colo4.com/status/
Updates were posted on Facebook and Twitter, so if you can't get to Muppet Central, it's always a good idea to check Facebook or Twitter for what's going on.