Firefox not working

Why is it saying this when I use Firefox?

http://prntscr.com/ixsq4o

You need to download "Silverlight" if you haven't already. If you have, the known browsers that work with SL are Internet Explorer and Safari

Firefox won't work unless you download an old version of Firefox (ESR) that still supports Silver Light.
You can download it here: https://www.mozilla.org/en-US/firefox/organizations/.

Napísal Noir Brillant, 29.03.2018 at 07:06

Firefox won't work unless you download an old version of Firefox (ESR) that still supports Silver Light.
You can download it here: https://www.mozilla.org/en-US/firefox/organizations/.

Thanks, I updated it and then it went all weird

Can you detail "it went all weird"?

You should not "update" your other (newer) Firefox version.
Just download and install a completely new and separate version (installation folder must be totally separate from your other versions. Consider it as a different software).
Anyways, it's working for me. I hope it will work for you.

Napísal Noir Brillant, 29.03.2018 at 13:10

Can you detail "it went all weird"?

You should not "update" your other (newer) Firefox version.
Just download and install a completely new and separate version (installation folder must be totally separate from your other versions. Consider it as a different software).
Anyways, it's working for me. I hope it will work for you.

I did not use firefox or IE for way over 2-3 years, was using SL with chrome for ages after they stopped it then just a few days ago SL does not work with chrome. Use firefox again, was working good with SL then 10-20 mins later "Firefox is out of date" so i update it, now says what it says in the screenshot