Thanks for your advice but I have tried what you have asked me to check (both of them) again (as Idid both before your advice came).
My problem is not solved. I can't play the videos at yahoo website. At the video site, the message in the rectangle area is always:
"You need Adobe Flash® to play this video.
Download the free Flash Player Now!
This is a known problem with Internet Explorer 11, which Microsoft has been aware of since October 18 when they released their latest "untested" browser. The pages can't recognize the browser, so they don't recognize any of the plugins, like Flash Player. So far, Microsoft has made NO indication that they have any plan to fix it soon.
Microsoft's recommendation is to use Compatibility View for affected pages, and "pretend" you're using an different browser. Trouble with that is it has seen limited success at best, and you have to individually enable it for EVERY page that has problems.
I'm not big on "pretending" so I recommend actually using another browser.
ANY of those will work where IE11 won't, with the Flash Player Plug-in (For all other browsers), and Chrome doesn't even need that because it has its own Flash Player plugin built in.