There is something really weird happening with my client's Firefox browser when I embed a Youtube video via Wordpress.
My client is running a windows 7 platform on a laptop that has 250GB Solid State Harddrive and 128GB Ram and Core i7. He says he never faces this issue when viewing videos on any other site.
Why would this be happening? Any idea?
Try adding "?wmode=opaque" to the end of the embed code.
I have seen this issue as well within WordPress and only on Firefox.
I have tested the embed code from YouTube and the one generated from WP (they are the same anyways) on a static HTML page with nothing but paragraph tags around the YouTube iframe embed and the issue still occurs.
Once I add in the "?wmode=opaque" param to the end of the iframe src url, the issue goes away.
Keep in mind that this will only work if you actually grab the YouTube embed code for the video and then add in this to the end of the URL, as the WordPress generated one will not pass it through.