I have been to the site and the problem with the navigation is completely gone. When attending to another matter wherein a website was redirecting me to other places, I had to do some virus/malware research. Turns out it was a virus on the host and not a problem at my end. I did learn something else about FF during my 3 or 4 hours wasted trying to sort out whether I had virus/malware.
I have several plugins installed and always update upon notification. I have noticed link and PDF problems for awhile. FF has a clean-myself-up function. From the menu HELP-TROUBLESHOOTING INFORMATION takes you to a utilities page that is presumably reading FF installation and telemetry data from your local installation. There is a give-FF-a-tune-up function. I have used this out of my virus/malware frustration. All is working again. No link problems and no stupid opening pdf in new tab BS. The internal PDF reader pops up, just like I remember it did in the past.
As I said I do have a few plugins and things were not right with FF. This has fixed my problems. Some may like to take a look. READ first what it does to your installation, configuration and data before giving it a go.
Cheers
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