Firefox recently removed support for some outdated, insecure versions of TLS. You should contact the owners of the website to ask them to upgrade to a newer version. Other browsers also plan to remove support for these versions in the future as well.

The website may try to fallback to TLS 1.0 in a way that is no longer allowed in current releases or may be using a deprecated cipher suite.

You can open the about:config page via the location/address bar and use its search bar to locate this pref:

• security.tls.insecure_fallback_hosts

You can double-click the line to modify the pref and add the full domain (TEXT) to this pref. If there are already websites (domains) in this list then add a comma and the new domain (no spaces). You should only see domains separated by a comma in the value column.

If this helps then you can contact this website and ask them to look into this.

• https://developer.mozilla.org/en-US/Firefox/Releases/36/Site_Compatibility#Security
• https://developer.mozilla.org/en-US/Firefox/Releases/37/Site_Compatibility#Security

Thank you both for your replies.

My user name of Thickoff was the nearest I could get to Thicko (sadly already taken) in recognition of my limited IT skills and comprehensive capabilities.

As such I can cope with user293's reply but am somewhat in awe of cor-el's reply!

The website in question is that of one of the UK's largest banks - I wonder if they will take any notice of me when I contact them?!

Thanks again for the replies

The website need to fix this and update their security to support TLS 1.2, so you ill have to contact them by email or phone.