Quote Originally Posted by Acorn View Post
If you designed and Previewed a lot in Edge then the browser cache needs to be purged with Ctrl+F5.

Acorn
Well, I was right about one thing: the problem was elementary. I had hit F5 and the "refresh" button so many times without effect and your suggestion instantly cured the problem, which was clearly how it appeared on my PC rather than to anyone else.

Many thanks for your help, Acorn - not for the first time.