I have Ubuntu 12.04 , I tried downloading the appropriate media player (VLC), but I still can't watch any video content.
The most reason would be to install Ubuntu extras. To do so, just press Ctrl+Alt+T on your keyboard to open Terminal. When it opens, run the command(s) below:
Try removing whatever you installed first:
sudo apt-get remove packageinstalled sudo apt-get autoremove
Then install this way:
sudo apt-get update sudo apt-get install vlc browser-plugin-vlc
This is what their site recommends: http://www.videolan.org/vlc/download-ubuntu.html. I recently installed it and can play .mp4 files on a fresh 12.04 install.