My youtube video is not displaying in full screen mode why?

My youtube video is not displaying in full screen mode why?hoe can i reset it?
Follow the steps to reset it:
1. Open your youtube video
2. Right clickk on video
3. Then click on setting. A small window will appear click on display
4. And chose Enable hardware acceleration, if it is already selected then disable it.
5. by follow the above rules your youtube video will always Run in Full screen mode.
enjoy>>>>>
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