Error could've showed up for a variety of reasons. DNS, issue with the httpd conf file, etc. They're outlined in the wiki:
I can verify myself that the site is coming up, but then again, it could be because the issue was fixed in the config or my location. If you're still seeing the error, it might be related to DNS, so it give it a few hours before things resolve correctly for you. If the issue still persists after a few hours, let our support know and they can take a look at things for you.