For this to work you need to set in the properties of the Youtube Object in General-> Support both Flash and HTML5 this will then set the Object to use a iframe which the css below requires.
Please note that this only works if you are just using it as a embeded player it does not work with the lightbox feature.
Before: After: The CSS:
Code: Select all
<style type='text/css'>
iframe {border:20px solid #000;
border-radius: 20px !important;
}
</style>