Are they crazy? You have the latest version.

have the latest version but still can not sign in due to the blue screen can not do anything as the site is dead.

Hi, have you tried to start Firefox's troubleshooting mode yet? If you haven't already, you can type in the about:support bar and from there activate the troubleshooting mode. Once you've done that try browsing the Tesco Bank site again, if you don't encounter any problems that way it probably means that there is an extension creating a conflict with the site... Let me know if you still experience problems with the troubleshooting mode active