As others have stated we seem to have a problem reaching the http://beta.developer.mozilla.org/ URL from outside the USA.
I’m able to access it without issue when using Tor with an exit node in the US.
Yesterday as soon as the post went live I was able to access Beta MDN from here in Germany without an issue.
However, as the others mentioned it seems we’re having connectivity issues for those of us outside the US.
> traceroute -d http://beta.developer.mozilla.org/
> traceroute: unknown host http://beta.developer.mozilla.org/
> ping http://beta.developer.mozilla.org/
> ping: cannot resolve http://beta.developer.mozilla.org/: Unknown host