Check it out here: http://rp.eliteskills.com/html5.php It's a basic old school style RPG MAP that supports multiple users using HTML5 Websockets for the client and erlang for the server.
jimmyrcom/HTML5-Canvas-Old-School-RPG-Map-with-Erlang-Websockets-Chat
You can make MMOs now using html thanks to google. See the link for what it does. The client is pure HTML5, the server here is erlang.
Erlang