CSS-only drop-down menu items showing through - css

Question

I'm trying to get a CSS-only drop-down menu working. It largely does work except for the fact that other content appears to be showing through and I can't work out why.
http://jsfiddle.net/uQveP/4/
Could someone tell me what I'm doing wrong? CSS not my strong suit.
The drop-down is appearing in the correct position, but you can see the other "test" links showing through. In the image, the bottom two "test" links should be hidden by the presence of the dropdown.
TIA

Answer 1

(2nd attempt)
Ok, if I understand correctly all you need to do is move the z-index to the ULs:
.drop-menu-header ul, .drop-menu-content ul {
margin: 0;
padding: 0;
list-style-type: none;
float: right;
text-align: right;
}
.drop-menu-header ul li, .drop-menu-content ul li {
display: block;
position: relative;
/*POOF*/
}
.drop-menu-header ul li ul, .drop-menu-content ul li ul {
display: none;
right: 0;
/*SHAZAAM!*/
z-index: 5;
}
.drop-menu-header ul li a {
display: block;
white-space: nowrap;
color: #fff;
}
.drop-menu-content ul li a {
display: block;
white-space: nowrap;
}
.drop-menu-header ul li a img.fake-button, .drop-menu-content ul li a img.fake-button {
padding: 0;
}
.drop-menu-header ul ul li a, .drop-menu-content ul ul li a {
padding: 5px 15px;
}
.drop-menu-header span {
padding: 5px 15px;
display: block;
white-space: nowrap;
color: #fff;
}
.drop-menu-content span {
padding: 5px 15px;
display: block;
white-space: nowrap;
}
.drop-menu-header ul li span a, .drop-menu-content ul li span a {
padding: 0;
display: inline;
white-space: nowrap;
}
.drop-menu-header li:hover ul, .drop-menu-content li:hover ul {
display: block;
position: absolute;
border: 1px solid #999999;
}
.drop-menu-header li:hover li {
float: none;
background-color: #5c87b2;
}
.drop-menu-content li:hover li {
float: none;
background-color: #fff;
}