when posting youtube code you don't post the whole url only the code
in the above I removed everything but:
So looking at a youtube video the url looks like this
http://www.youtube.com/watch?v=Qc14sBWU06c
All you need is the Qc14sBWU06c between our youtube brackets which are yt minus the ['s
hope that helps guys, I wish you could do a better job of detailing instructions on the bbcode page.