Just for completeness... When I installed my Linux Firefox, I copied my windows profile over so I had the same (initially) bookmarks and passwords. Is there likely to be a profile issue? That is the only common thing between both installations.

Additional. BOTH windows and Linux were scrolling this web site happily for some time. The transfer of profiles was done over a year ago, with no further exchanges between platforms.

Both windows and Linux browsers have been updated.

I have yet to try creating a new blank profile.

Note that some files may contain absolute file path, so copying a full profile across different operating systems is not recommended. Some files that may contain such paths include pkcs11.txt and extensions.json and prefs.js. Best is to copy only database files that contain valuable personal data.

Thank you for your reply cor-el. Both of my machines behaved perfectly with this one site long after I copied the profile from the windows Firefox, to my Linux version, so I am tempted to assume a Firefox update has reacted unfavorably.

What I cannot understand is how, when I switch ALL the protection off, I still cannot scroll this ONE page. I do not understand what has been detected by the firefox protection to turn the shield blue in both cases.

There had to be some code that says IF (condition); Turn the shield blue... I only have the issue with firefox.

You can check the Web Console (Tools -> Web Developer) for messages about content blocked by Tracking Protection.

• https://firefox-source-docs.mozilla.org/devtools-user/web_console/

You can check the Network Monitor to see if content is blocked or otherwise fails to load.

• https://firefox-source-docs.mozilla.org/devtools-user/network_monitor/

If necessary use "Ctrl+F5" or "Ctrl+Shift+R" (Mac: Command+Shift+R) to reload the page and bypass the cache to generate a fresh log.

Excellent.. Something I can try.. MANY thanks.. I will report back... Well. That was interesting. I can see what appear (To me), to be error messages as there is a lot going on..... UNFORTUNATELY, I don't have a clue how to decipher and act on these.

I HOPE the attached image that shows all the errors, inspires you

At one point, I had an error reporting duckduckgo blocking something, so I changed to google and that message has gone away.

Just so that we are clear, ONLY this rapid electronics web site behaves this way, a blue shield and unable to scroll. IF there are other web sites that misbehave, I have yet to find one.

I did try adding an exception but that didn't fix it...

I FIXED IT. It also fixed another web site where I couldn't; log in..Though no one will like what I did.

I copied by alleged broken profile on to the desktop so I could delete my Firefox profile in Linux, and rename the default preferences to the same as the file I coped out. I started Firefox and noted the troublesome site would now scroll.

NEXT. I copied every folder, one by one, into the Firefox default profile running Firefox at ever single change noting all was still OK. At the same time, I checked my other odd site and noted I could log in properly...

NEXT, I copied all the files, one by one except where there were a group of files with the same name but different extensions. Still OK. The exception was prefs.js where the default was just ONE file. My "alleged broken" profile has another eleven (11) prefs.js files... I didn't copy these over.

SO, I went from a broken profile (being common with my windows profile a long time ago, to an EXACT copy only missing erroneous prefs.js files, and it all works.

I STILL have the BLUE shield on this ONE web site but, it scrolls and other functions work too.

SO, it appears that the act of copying the profile out, renaming the default profile and copying all the files back in, has fixed it.

I did say you wouldn't like the answer.

As my windows Firefox remains broken at this time. I cannot copy my Linux profile over to my windows profile as windows contains login data I don't want shared on my Linux system, so I shall do the same file copying scenario next time I have that machine on.

Unsatisfactory from a bit, byte, nibble, viewpoint, but at least a fix. Could the plethora of prefs.js files be the reason?

I COULD copy the remaining prefs.js files over and check but as I do not know how to interpret these files, it might be a waste. QUESTION, does Firefox use JUST prefs.js and/or why would it create files up to (on my system), prefs.js-11?

Merry Xmas to all my readers. and many thanks to cor-el for at least reaching out.

You only need one prefs.js file and not any numbered prefs-##.js files are those are the result of Firefox being unable to rename a numbered prefs-##.js temp file to prefs.js.