Why am I getting a CAPTCHA message without a CAPTCHA when I attempt to login to Steam?

Solution 1:

If there's no CAPTCHA and you're getting this message, this is usually a (very poorly worded and completely unhelpful) error message indicating that the system is down for maintenance.

The Steam Downtime Annoucement thread on the Steam forums seems to confirm this is the likely culprit. If you go to the last page of that thread, it mentions some downtime today around this time.

Give it a little while, and then try to login again.

Solution 2:

If you've failed to login two or more times, the site usually displays a CAPTCHA below the password field. That's what the error seems to indicate.

However, there's a good chance that logins are failing due to maintenance that Valve is doing on their servers today (originally scheduled for 1600 PST, but Valve time...).

P.S. You may be able to log in via the Steam client instead.

P.P.S. I am currently unable to log in through the web store either, but I got past the username/password screen to the Steam Guard screen, which just loops endlessly once I enter the code: