Yesterday Steam’s Winter sale went live, and today the service went down. As of writing this article, steam is completely down for everyone. You can check if steam is down now or not from this website.
Still now there is no news from Valve regarding this down time. As we’re entering into the holiday weekend it’s very possible that, while engineers are likely working hard to make sure the servers get back up in a timely fashion, we cannot say the same for responses to press inquiries.
Your purchases will have to wait, and your voting for the Steam awards will have to take some rest to the act of living the rest of your life. We hope for the return of Steam soon, or at least for some official news from Valve about what is going on, and when we can expect it back.
For more updates regarding steam is down, please check Steam thread on Reddit.
Update 23-12-2016: Steam is working now!