The Friends server will be down for the next day or so while we make improvements to it.
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Some people might be getting the following message when attempting to login to Steam:

"Login to steam failed. Either the specified account does not exist, or the password was wrong. Please check your email address and password and try again."

This is a bit misleading - your account exists and is fine. The authentication servers are under heavy load right now. This problem should be resolved shortly. Thanks for your patience!