I am using Ubuntu 13.04 and I cannot watch movies online with my Firefox. I have tried installing Flash player for Windows, but it won't start installing.
First,I don't understand Windows Firefox in Ubuntu. So, I make an assumption that you are running Firefox which came preinstalled with Ubuntu. I suggest that you download the Adobe Flash plugin from the Ubuntu Software Center:
Note that this is the last official version you will get. You can also try Gnash, if you wish.
There is easy 2 steps. You can solve your problem.
1st: Update your adobe flash player. 2nd: Clear your browser cache and cookie.
Another solution is, Watch Movies or TV Show Online video third party streaming server.