Got my Vista + Firefox showing videos in posts again.
Vista + Firefox 43 was not giving me the update option when clicking About Firefox
option. So I had go to Firefox website to get newest version - 52. Seem version 52 will be last supported version for Vista, "Firefox version 52 will be the last complete update for Windows XP and Windows Vista. Security updates will be released, but no new features".
And I did not loose my many, many bookmarks and was able to Restore Previous Session to get my 100+ tabs back.
I always worry doing an update, going screw things up and sometimes I don't like the new features.
Now hopefully missing youtube bug won't show up again before my current 5 year old gaming computer becomes my surfing computer in 2018 and I finally say goodbye to Vista.