We'll be performing routine maintenance on some of the Steam servers on Tuesday October 2, 2012 around 16:00 PDT (GMT-0700).
Chat, game lobbies, and the community web site will be affected for the duration of this maintenance. Some content downloads may be briefly interrupted. Game play should generally not be interrupted but may be impacted for some multi-player titles.
We'll also be performing routine network maintenance on Tuesday October 2, 2012 at 21:00 PDT (GMT-0700). The Steam store and community web sites will be unavailable for approximately 15 minutes at this time, but other services will be unaffected.