That is someone else's login name...
I can't see the far right of your page as your screenshot doesn't extend far enough.
Is this a personal computer and is there someone in your family that uses that login name on any other website? If yes, then, on the right hand side of the page, when you see this, you will see the option to "log out". Do that, then clear your browser's cache. Then when you log in you should have no problems and it should recognize you and you won't see that message.