You might want to make different plans for Thursday if you intended on playing Left 4 Dead 2 or any game relying on Steam matchmaking and lobbies. Valve is planning on performing scheduled maintenance on Thursday beginning at 6PM PST; they expect it to take no longer than three hours, setting a return to normal operations by 9PM PST. You'll still be able to play any of the games you own on Steam, but those that rely on Steam matchmaking, including L4D2, will be unplayable.
Other services will be unavailable as well, including Steam Community, downloading games from Steam, and purchasing games from the Steam store.
more here
Other services will be unavailable as well, including Steam Community, downloading games from Steam, and purchasing games from the Steam store.
more here