Server Crash

Whenever i try to join a server it says

failed to login: java.io.IOException: Server Returned HTTp response code: 503 for URL: http://session.minecraft.net/game/joinserver.jsp?user=Deadlyminer12&sessionId=token%3Abecd5c47d41c4e6b38a5eada3fe57f7%A3049d125faa84df994536add88fb1815&serverId=289b78b6d8af402ceed7344afb1c386e02df1b50

thats all it says