add wmode=transparent to the youtube URL:
<iframe width="640" height="360" src="http://www.youtube.com/embed/5yh6L4IU6OA?rel=0&wmode=transparent" frameborder="0" allowfullscreen></iframe>
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.