Sometimes pages contains objects such as flash objects, select boxes, iframes, applets, etc. DHTML objects (e.g. submenus) are shown under them because of these objects always have a higher z-order.
    DHTML Menu Sample can drop down sub menus over all the objects of the page. If for some reasons a sub menu can't drop down over an object the last will be hidden for a time when the submenu is shown.

Set the following menu parameter to enable checking of intersection with iframes, movies, selects:

var dmObjectsCheck = 1;

Fix for flash in Firefox!
    If you don't want that flash will be hidden under submenus in Firefox you should do the following things:

1) Use the latest engine files v3.0.
2) See, how you should install flash on your pages.
<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,0,0" height="150" width="732" name="if-header">
     <param name="movie" value="images/flash/if-header.swf">
     <param name="quality" value="best">
     <param name="play" value="true">
     <param name="wmode" value="opaque">
<embed height="150" name="if-header" pluginspage="http://www.macromedia.com/go/getflashplayer" src="images/flash/if-header.swf" type="application/x-shockwave-flash" width="732" quality="best" wmode="opaque" play="true">
</object>
Add "opaque" parameter for <object> and <embed> tags.
3) Set
var dmObjectsCheck=1;
4) Add the following function in the beginning of your data file

function dm_ext_ruleObjectHide()
{
// Safari detect
   if ((parseInt(navigator.productSub)>=20020000) && (navigator.vendor.indexOf('Apple Computer') != -1) && (navigator.product=='Gecko'))
     return true;
   else
     return false;
}