Steam has a worldwide service, store halt. The servers are down and players can neither go online nor can they play some single-player games, let alone buy new games in the Steam sale.
Many enraged gamers have messaged valve regarding the down time but so far it seems that there is no response. Although an update from valve about the situation may be out soon.
So far, steamstat.us, an official checker for Steam’s services, can be used to check whether or not the services are up. Steam being down brings millions of gamers unable to enjoy their holidays.