You all but have it. The only thing you are missing is that for z-index to work, it has to be applied to a div whose position has been explicitly set to absolute, fixed or relative.
Check this out: http://jsfiddle.net/panchroma/eyccd/
The code is exactly the same as what you had started, I just tweaked this CSS:
.callouts {
position:relative; /* <======= added this */
display:block;
margin-top: -150px;
z-index: 999999999999999;
}
Hope this helps!