span.menu {
position:relative;
height:16px;
background : lime;
border: solid 1px;
margin: 1px;
z-index:+1;
}
span.menu:hover {
background : green;
position:relative;
z-index:+1;
}

span.menu div.hide{
position:absolute;
visibility:hidden;
left:0px;
top:16px;
}
span.menu:hover div.hide{
position:absolute;
visibility:visible;
background : lime;
left:0px;
top:16px;
}

.pop_target{
position:relative;
}
.pop_target .popup{
position:absolute;
visibility:hidden;
left:50px;
top:40px;
}
.pop_target:hover .popup{
position:absolute;
visibility:visible;
left:50px;
top:40px;
z-index: +1;
}