UPDATE: Valve is aware of this issue and are working to fix it. It's a problem with steam authentication. In addition some other games using the same steam authentication system are experiencing this issue.[/b]
Some users can connect, some can't, sometimes resetting steam works, sometimes it doesn't. We will let you guys know exactly what is going on as soon as we can. Thanks a bunch for being patient and sorry about the downtime.
UPDATE 2 : We're attempting to restart some of the servers, this means the server you are playing on may go down for a few minutes