Hi Alpha_Data, this is not a change in Firefox, so we need to look for another explanation.

I noticed your have an extension named "IObit Surfing Protection & Ads Removal 2.1.2". Anything like Surfing Protection, Home Page Protection, Browsing Protection, etc., can indicate an add-on or external function to lock your settings and revert them at startup. Please look into disabling that feature.

This article lists other possible explanations for settings to be lost/reverted between Firefox sessions: How to fix preferences that won't save.

Can you track down the culprit?

You also seem to have/had Advanced SystemCare.

• Advanced SystemCare Surfing Protection 2.0 (disabled)

Advanced SystemCare with its Surfing Protection feature can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software.

Thanks guys I appreciate the input. Both were not helpful. But while reading "How to fix preferences that won't save" it directed me to the meaning of "user.js", which I had noticed when I was doing troubleshooting b4 posting my question.

Mozilla indicated that the "user.js" was installed by microsoft so I thought it was all good. Once I learned that it takes precedent over selections I quickly renamed it and presto, all my problem vanished except the fixed default check for Firefox. I am assuming that it is Firefox doing that I can't change that ... right?

Alpha_Data said

Mozilla indicated that the "user.js" was installed by microsoft so I thought it was all good.

No, neither Mozilla nor Firefox would be able to identify the creator of a user.js file. I don't know where you got that idea. If we need to edit one of the knowledge base articles to correct that, please indicate where it appears.

If you mean that Windows Explorer said it was a Microsoft JScript type file, that relates to the default application for opening (executing) the script, and not the source of the file.

Once I learned that it takes precedent over selections I quickly renamed it and presto, all my problem vanished except the fixed default check for Firefox. I am assuming that it is Firefox doing that I can't change that ... right?

I've had "Always check if Firefox is your default browser" turned off for as long as I can remember on Windows 7 and earlier. You should be able to modify that setting. The article I referred you to before lists other possible sources of this problem that you could investigate.

I rarely use Windows 10, and that OS has a different way of determining default applications than earlier versions. To select a different default browser, see this article and select the one you prefer: How to change your default browser to Firefox on Windows.

jscher 2000 said ... "If you mean that Windows Explorer said it was a Microsoft JScript type file, that relates to the default application for opening (executing) the script, and not the source of the file."

My bad! I misread it. I thought it was talking about the file itself. You do know that Microsoft is battling to make the "Edge" the top browser?

Yeah, I thought it would be very aggressive of Firefox to hard select that. But with the invasive nature of software packages (e.g., google, etc.), I thought FF was trying to protect its turf. Mind you, I don't want to change the default, but I would like it to be my option.

I will read the article later.

Thanks again, jscher 2000, your dedication is very much appreciated.