This has been discussed elsewhere but not using NOF13 and HTML5.
I've uploaded the bad page to http://www.solarlightcap.com/test/index.html
You will see the submenus appear below other elements - an image or a layout region containing wowslider
It was okay using NOF13 before I changed to HTML5. I've fiddled with the z-index value of various elements without success.
A real mystery I hope someone can solve.
As a small aside using http://validator.w3.org/, it observes that my charset is generated wrong even though I changed it to UTF-8 as one should for HTML5
It says Warning Line 5, Column 27: Using windows-1252 instead of the declared encoding iso-8859-1.
<meta charset="ISO-8859-1">