Some HTML5 videos (especially Vine videos) won't play on Windows. You can quickly work around this issue by changing a Windows Media setting.
- Type about:config in the address bar and press EnterReturn.
A warning page may appear. Click to go to the about:config page. - Search for: media.windows-media-foundation.enabled.
- Double-click the setting to change its value to false.
- Finally, reload the page with the video and it will work.
This workaround should cause the website to give you a Flash video. If you don't have Flash installed, see Install the Flash plugin to view videos, animations and games.