I find the following feature of Norton very annoying:
If I go to a website where I have set up more than one login, then of course Norton shows all the logins. However, if the one I want to use has already been filled in by Norton (i.e. I don't want to select one of the alternatives), I then click Sign In (or Login, or whatever button the website has) and nothing happens. Why? - because the Norton bar that says "Which login would you like to use" has disappeared and in doing so has moved everything on the page up, so that my mouse cursor is no longer over the login button. I then have to press the button again to log in.
Surely it can't be beyond the wit of man to design the multiple choice login id display so that it doesn't involve shifting everything down when the "Which login would you like to use" bar appears and then shifting everything back up again when it disappears?