Heres basic example what you are after. Little bit of javascript and css:
<html>
<head>
<title>test</title>
<style type="text/css">
<!--
#mydiv {
position: absolute;
background-color: #dddddd;
width: 150px;
height: 150px;
display: none;
top: 50px;
left: 50px;
}
-->
</style>
<script language="javascript">
<!--
function display(id,disp) {
var div = document.getElementById(id);
div.style.display = disp;
return false;
}
-->
</script>
</head>
<body>
<div id="mydiv">Heres some content blah blah</div>
<a href="" onmouseover="display('mydiv','block');" onmouseout="display('mydiv','none');">Hover over me!</a>
</body>
</html>
I created that display function but you could live without it. You could do the link like this(althought the display-function is nicer IMO):
<a href="" onmouseover="document.getElementById('mydiv').style.display='block';" onmouseout="document.getElementById('mydiv').style.display='none';">Hover over me!</a>