Hey, team lead for the #XMPP Standards Foundation infrastructure team here.
The server that handles XSF web (xmpp.org, wiki.xmpp.org, xmpp.net) and chatrooms (muc.xmpp.org) went down early on 2020-03-20. The cause is currently unknown, we are awaiting a response from the hosting provider.
Meanwhile we have already restored wiki.xmpp.org onto a new server from our latest nightly backups, and other services will follow as soon as possible.
Please be kind to everyone in these difficult and disruptive times!