проблему решил сам
<html>
<head>
<style type="text/css">
<!--
.zn_fon_1{background-image: url(fon_1.jpg);background-repeat: no-repeat;}
.zn_fon_2{background-image: url(fon_2.jpg);background-repeat: no-repeat;}
.zn_fon_3{background-image: url(fon_3.jpg);background-repeat: no-repeat;}
-->
</style>
</head>
<body>
<table width="700" height="374" border="1" cellpadding="0" cellspacing="0">
<tr>
<td width="200">
<ul>
<li><a href="#" onClick="showmetka(1,50,100)">фон_1_50_100</a></li>
<li><a href="#" onClick="showmetka(1,50,50)">фон_1_50_50</a></li>
<li><a href="#" onClick="showmetka(2,100,50)">фон_2_100_50</a></li>
<li><a href="#" onClick="showmetka(2,70,150)">фон_2_70_150</a></li>
<li><a href="#" onClick="showmetka(2,157,210)">фон_2_157_210</a></li>
<li><a href="#" onClick="showmetka(3,38,200)">фон_3_38_200</a></li>
</ul>
</td>
<td width="500" align="left" valign="top" id="zn_fon">
<div name="metka" id="metka" style="visibility:hidden; display:none; position:relative;"><img src="metka.png"></div>
</td>
</tr>
</table>
</body>
</html>
<script language="javascript">
<!--
function showmetka (fon,top,left) {
td = 'zn_fon_'+fon;
div = 'm_'+top+'_'+left;
var tdimg = document.getElementById("zn_fon");
tdimg.className = td;
var divimg = document.getElementById("metka");
divimg.style.visibility = "hidden";
divimg.style.display = "none";
divimg.style.top = top;
divimg.style.left = left;
divimg.style.visibility = "visible";
divimg.style.display = "block";
}
//-->
</script>