Cmq, così, per non aver nulla da fare… ti ho semplificato di brutto quello che stai già facendo… 
codice:
<!doctype html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Draggable objects</title>
<script type="text/javascript">
var bMouseUp = true, oDragging, nMouseX, nMouseY, nStartX, nStartY, nZFocus = 100 /* the highest z-Index present in your page plus 1 */;
function dragDown(oPssEvt1) {
var oMsEvent1 = oPssEvt1 || /* IE */ window.event;
oDragging = oMsEvent1.target;
if (oDragging.className !== "draggable") { return; }
bMouseUp = false;
nStartX = nStartY = 0;
for (var iOffPar = oDragging; iOffPar; iOffPar = iOffPar.offsetParent) {
nStartX += iOffPar.offsetLeft;
nStartY += iOffPar.offsetTop;
}
nMouseX = oMsEvent1.clientX;
nMouseY = oMsEvent1.clientY;
oDragging.style.zIndex = nZFocus++;
return false;
}
function dragMove(oPssEvt2) {
if (bMouseUp) { return; }
var oMsEvent2 = oPssEvt2 || /* IE */ window.event;
oDragging.style.left = String(nStartX + oMsEvent2.clientX - nMouseX) + "px";
oDragging.style.top = String(nStartY + oMsEvent2.clientY - nMouseY) + "px";
}
function dragUp() { bMouseUp = true; }
function keyListener(oPssEvt3) {
var oKeyEvt1 = oPssEvt3 || /* IE */ window.event;
if (oKeyEvt1.ctrlKey && oKeyEvt1.charCode === 109) { // ctrl + m
document.getElementById("votazione").style.display = "block";
}
}
document.onmousedown = dragDown;
document.onmousemove = dragMove;
document.onmouseup = dragUp;
document.onkeypress = keyListener;
</script>
<style type="text/css">
.draggable {
position: fixed;
left: 0;
top: 0;
width: auto;
height: auto;
cursor: move;
}
#votazione {
width: 300px;
height: 200px;
left: 200px;
top: 200px;
background-color: #00ff00;
display: none;
}
</style>
</head>
<body>
Premi ctrl + m !!</p>
<div class="draggable" id="votazione">Hello world!</div>
</body>
</html>