YouTube

Hey, I'm trying to download videos from YouTube to but onto an iPod. I have got the addon from Mozilla that lets you DL youtube videos, yet when i am on the video i would like to download, I click the DL tab on my browser, but a pop up comes up stating that youtub.com/XgjGj8H8 is not a supported link.
Im not sure what next to do, so any help would be greatly appreciated.
Thanks.
Im not sure what next to do, so any help would be greatly appreciated.
Thanks.