I’m not quite sure what you are attempting to do as you only seem to have one drop down menu item and it is visible at all time. Usually you would hide it off screen with absolute positioning and then bring it back when you need it.
e.g.
#navwrap ul li{position:relative}
#navwrap ul ul{
position:absolute;
left:-999em;
z-inex:10;
}
#navwrap ul li:hover{z-index:99}
#navwrap ul li:hover ul{left:0}