怎么样可以将导航条置于鼠标点击的坐标位置？

点右键：
<html>
<head>
<STYLE>
.skin0 {
BORDER-RIGHT: black 1px solid; BORDER-TOP: black 1px solid; VISIBILITY: hidden;
BORDER-LEFT: black 1px solid; WIDTH: 150px; CURSOR: default; LINE-HEIGHT: 1px; BORDER-BOTTOM:
black 1px solid; FONT-FAMILY: Verdana; POSITION: absolute; BACKGROUND-COLOR: black; TEXT-ALIGN:left
}
.skin1 {
BORDER-RIGHT: buttonhighlight 0px outset; BORDER-TOP: buttonhighlight 0px outset;
FONT-SIZE: 9pt; VISIBILITY: hidden; BORDER-LEFT: buttonhighlight 0px outset; WIDTH: 120px;
CURSOR: default; BORDER-BOTTOM: buttonhighlight 0px outset; FONT-FAMILY: Arial, Helvetica,
sans-serif; POSITION: absolute; BACKGROUND-COLOR: #000000; TEXT-ALIGN: center
}
.menuitems {PADDING-RIGHT: 10px; PADDING-LEFT: 10px}
</STYLE>
</head>
<script>
function showit(){
var display_url="0"
var rightedge=document.body.clientWidth-event.clientX
var topedge=document.body.clientHeight-event.clientY
if(rightedge<dandan.offsetWidth)
dandan.style.left=document.body.scrollLeft+event.clientX-dandan.offsetWidth
else
dandan.style.left=document.body.scrollLeft+event.clientX
if(topedge<dandan.offsetHeight)
dandan.style.top=document.body.scrollTop+event.clientY-dandan.offsetHeight
else
dandan.style.top=document.body.scrollTop+event.clientY
dandan.style.visibility="visible"
return false
}
function hiddenit(){
dandan.style.visibility="hidden"
}
function spring(){
if (event.srcElement.className == "menuitems") {
if (event.srcElement.getAttribute("target") != null)
window.open(event.srcElement.url, event.srcElement.getAttribute("target"));
else
window.location = event.srcElement.href;
   }
}
function lowlightie5(){}
function highlightie5(){}</script>
<body>
<div id="dandan" class="skin0" style="Left:280;Top:28;" onclick="spring();event.cancelBubble=true" onmouseout=lowlightie5() onmouseover=highlightie5()>
<ul><center>
   <li><b>导航菜单<b></li>
   <li><a href="http://www.163.com">论坛</a></li>
   <li><a href="http://www.sohu.com">江湖</a></li>
   <li><a href="http://www.sina.com">电影</a></li>
   <li><a href="http://www.china,com">flash</a></li></center>
</ul>
</div>
<script>
if(document.all && window.print){
dandan.className = "skin1";
document.oncontextmenu = showit
document.body.onclick = hiddenit;
}
</script>
</body>
</html>