What ever this is, disabled Firefox and I do not how to fix problem, Error: Platform Version '50.10 is not compatible with- Min Version.=43.0.4 Max Version,=43.0.4. I would appreciate any help. I have gone back to Internet Explorer, but I would sure like to have Firefox back.

Try uninstalling and reinstalling Firefox.
If that doesn't work, try setting Firefox preferences to default.
If Firefox won't start, you can try deleting the profile folder in
C:\Users\your-username\AppData\Local\Mozilla\Firefox\Profiles\3t85k562.default
The 3t85k562.default folder would be the profile, and it will have a different number before the .default part. That number different with every installation.

Firefox should create a new profile automatically when you restart it after deleting the 3t85k562.default folder.
But if it doesn't, you can always uninstall and reinstall and that will create a new (uncorrupted) default profile.

You might want to try to export your bookmarks before you uninstall or delete the profile folder (assuming Firefox starts).
https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Jenny100, Is the Firefox Stub download the same as the regular download? I remember reading about that here, but I can not for the life of me find the post.

Jenny said in an older post:

Marian, Thank you.

You're welcome.