Mozilla Firefox "Not Supported" error message.

windowsMe

Commendable
Nov 21, 2016
28
0
1,540
Hello
When I try to go to play you tube videos on my Windows vista computer, I get an error message that says "Oops, your browser is no longer supported." I'm running Mozilla Firefox 50, and it's up to date. Is it that some add-on is hijacking my browser?
Thanks in advance