No worries we can solve this by installing “restricted extras” in Xubuntu. The “restricted extras” is a package that not only contains flash, the thing needed to play youtube videos, but also other goodies like codecs for example. Codecs are needed to be able to play all your movies and songs stored on your harddrive.
Open terminal and type:
sudo apt-get install xubuntu-restricted-extras
After a while you will be asked if you want to continue:
After another while you will see this screen.
Press the tab button to highlight the <ok> and hit enter.
Then you’ll see this screen:
Press tab again to higlight <Yes> and hit enter.