I just logged on as someone else

[Beyond Rational]

I just clicked on the general gassing button to find "Welcome Back squeakyD" and the appearance different to my setup, which was weird.

[Mr Will]

This is an ongoing problem which has been discussed in depth before (see HERE In short, it's a bug with out caching systems which causes the wrong version of the page to be displayed to certain users.

You are not actually logged in as them and cannot do anything or see anything which is not public already so it is not a security risk and simply refreshing will get you back to your version.