Where in the browser is this happening? The browser or a website? *[[How do I create a screenshot of my problem?]] If this is happening in Hello, the built in chat to Firefox 35 it is possible to sign out of Firefox accounts from accounts.firefox.com. If it is happening in a website, please clear the cache and try to access the site again. If there is another user that also uses the computer it is possible that their user name was still there.