Q: iweb youtube URL is invalid

Have you tried using the YouTube widget or copying and pasting the full code into an HTML Snippet?

http://www.iwebformusicians.com/Website-Movie-Video/Vimeo-YouTube.html

"I may receive some form of compensation, financial or otherwise, from my recommendation or link."

I'm having the same problem. 

Bonjour

Make sure that the video can be shared

I noticed this problem happening a couple of updates or so ago. I simply Started using the HTML Snippet with the share code from YouTube not glamourous but, it works.

Because Youtube gives a redirection link

Look at this page http://www.youtube.com/watch?v=wrivjzw0RlI

the link to shared is

http://youtu.be/wrivjzw0RlI

If you paste this link in a iWeb YouTube widget, you will see nothing

In a browser, this link redirects

http://www.youtube.com/watch?v=wrivjzw0RlI&feature=youtu.be

delete &feature=youtu.be

and you have the url of your page (my first link) that you can copy and paste in a widget

"Change is only good when it makes things better."

The embed code is what you need in order for the HTML Snippet is concerned however on the video above this feature has been disabled. Which, could also be the issue with the YouTube widget within iWeb

This works! Cheers Koeklin