try testing using FireFox instead of internet explorer, it may give you a better error message with more information.
Do you have a link where I could test the issue to get a better understanding of what is going on?
As for the F12 preview, if you have previously tested the page, and logged in, the browser session will not cleared (you will not be logged out) unless you close the browser completely. You must close all instances of your browser to end the session.