If you turn off Bitdefender what happens? I run Kaspersky on Win7 and Win11 with no issues.

I've got Windows 10, I had no problems with Kaspersky, but I've changed because of the current situation, although, as a personal user, chances are that it's a very small risk.

I switched off the anti virus on Bitdefender, but it makes no difference.

Can you post screenshots of the issue and provide a link(s) to replicate. https://www.bbc.com/news/av/world-europe-60853404

Have you tried Firefox in Safe Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#w_how-to-start-firefox-in-4troubleshoot-modesf5safe-modesf

The troubleshooting mode makes no difference. I've attached a screen grab of a BBC page showing the issue.

Did you turn off Bitdefender or Disable?

I only turned off the Anti virus part of Bitdefender, it's not as easy as Kaspersky to disable, I'll have to look it up.

Here is what I found. https://www.bitdefender.com/consumer/support/answer/28557/

Thanks, unfortunately, I have to go out now for the evening, so I'll have to continue this tomorrow.

.....

I've solved this issue. I cleared out the Firefox cache and the BBC site is now working as before.

Many thanks for your help.

Good. Mark it as resolved and have a good day.