There are a few pages that describe the issue and offer a solution but after reading them I didn’t quite get it. I hope it’s not me being dumb but I just don’t think that the fix was described in simple terms.
The issue: sorry I can’t show screen shots as the site is private but the issue is the classic drop down navigation slides down and then disappears behind an element on the main page. My initial attempts to fix the error all focused on the component parts of the navigation. I started adding huge z-index numbers to the UL’s and then the LI’s of the navigation but still no change.
The fix: in simple terms you should apply your high z-index number to the element which surrounds the navigation, in my case a div called “navigation”.
<div id="navigation"> <ul id="mainnav"> <li>Home</li> <li>Contact</li> </ul> </div>
If that doesn’t solve the issue then I would recommend concentrating on the parent elements and don’t get sucked into the child elements.