After embedding a Youtube video on the front page, I noticed that the drop down menus were appearing behind the video, making some pages inaccessible from the menus. Not good.
Some poking around Google led to http://manisheriar.com/blog/flash_objects_and_z_index
I found that only step 3 (setting wmode=”transparent” in the embed tag) is necessary. To get that version of the embed code, it is necessary to select the “Use old embed code” checkbox in Youtube’s embed settings. However, this means that only Flash playback is supported.
Prior to this, I also tried wrapping the embed code in a <div> and using the z-index CSS setting. That didn’t work at all. Perhaps there’s another solution that will work with the iframe embed method so HTML5 video can also be supported.