I made some threads about problems playing webm videos on firefox and I have discovered that first of all firefox hugs to much resources because Google chrome plays webm much better.Found Webm Glitch/Bug that causes distortion in Youtube Videos.

Now I have discovered after many failed attempts to play webm that while the buffer bar is moving to complete the download it causes the video to break in formation ; when it completes buffering the video plays much smoother.

I took a screenshot of what I am viewing (basically my problem)

Note: The top portion of the video remains in order its only the bottom that breaks,and I have noticed that videos in 16:9 aspect ratio do much better than those of 4:3.

http://i42.tinypic.com/6fb1o5.png