Qualcosa del genere?
codice:
<html>

<head>
	<meta http-equiv="content-type" content="text/html;charset=iso-8859-1">
	<title>Prova</title>
	<style>
	<!--
	#maintab	{position: absolute; top: 0%; left: 0%; width: 100%; height: 100%; visibility: visible}
	#lay1	{position: absolute; top: 10%; left: 0%; visibility: hidden}
	#lay2	{position: absolute; top: 10%; left: 33%; visibility: hidden}
	#lay3	{position: absolute; top: 10%; left: 66%; visibility: hidden}
	//-->
	</style>
	<script language="JavaScript">
	<!--
	function setVis(id,vis) {
		window.document.getElementById(id).style.visibility=vis;
	}
	//-->
	</script>
</head>

<body bgcolor="#ffffff">
	<div id="maintab">
	<table width="100%" height="100%" border="1">
		<tr height="10%">
			<td  width="33%" onMouseOver="setVis('lay1','visible')" onMouseOut="setVis('lay1','hidden')">link1</td>
			<td  width="33%" onMouseOver="setVis('lay2','visible')" onMouseOut="setVis('lay2','hidden')">link2</td>
			<td  width="33%" onMouseOver="setVis('lay3','visible')" onMouseOut="setVis('lay3','hidden')">link3</td>
		</tr>
		<tr height="90%">
			<td  width="33%"></td>
			<td  width="33%"></td>
			<td  width="33%"></td>		
		</tr>
	</table>
	</div>

	<div id="lay1" onMouseOver="setVis('lay1','visible')" onMouseOut="setVis('lay1','hidden')">
	<table border="1">
		<tr>
			<td>tabella1</td>
		</tr>
	</table>
	</div>

	<div id="lay2" onMouseOver="setVis('lay2','visible')" onMouseOut="setVis('lay2','hidden')">
	<table border="1">
		<tr>
			<td>tabella2</td>
		</tr>
	</table>
	</div>

	<div id="lay3" onMouseOver="setVis('lay3','visible')" onMouseOut="setVis('lay3','hidden')">
	<table border="1">
		<tr>
			<td>tabella3</td>
		</tr>
	</table>
	</div>
</body>

</html>