I entered SuperUser via a standard Login. Then I couldn't Logout. There was no button or link to do that. I looked under the StachExchange sign at the upper-left, and all it produced was a message about visiting the Stack Exchange Network. I finally found a hidden link on the page by looking at the page-source (Firefox Cmd-U). It was this: 'https://superuser.com/users/logout' which seems like something that should be visible to the client.