As proposed at bug 35341 comment 3 (and supported at bug 35341 comment 4) and as mentioned again at bug 41484 comment 9, there's a head icon in the Vector and Monobook skins next to the username (or next to "Log in / Create account" while logged out) in the upper right corner of the browser window.
It's never been very clear to me what the purpose of this icon is beyond decoration. I think it can safely be removed from both skins.
Version: 1.21.x
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=41484