Si perdonami hai ragione.. Fino a ieri sballava sia su explorer che su mozilla firefox, adesso ho provato e su mozilla 3.6 funziona, su explorer 8 no..

index.htm
codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">

<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Nichiweb.com</title>
<link rel="stylesheet" media="screen" href="style.css" />
</head>

<body>
<div id="testata">
 <table id="table-testata">	
	<tr><td id="test3"> </td></tr>
    <tr><td id="test2"> </td></tr>
	<tr><td id="test1"> </td></tr>
    <tr><td id="test0"> </td></tr>
 </table>
</div>

<div id="main">
Main
</div>

<div id="menu">
<table id="table-menu">	
	<tr>
	 <td id="test-menu"> </td>
	</tr>

        <tr>
	 <td id="content-menu">b</td>
	</tr>
</table>
</div>

</body>
</html>
style.css
codice:
/*
Theme name: Nichiweb
Version: 1.0
Url: http://www.nichiweb.com
Description: Primo tema sviluppato per il sito Nichiweb.com
Author: Nicoletta Giacalone
Tags: colonne, organic, paper, magazine
*/

body {
	background-image: url('images/struttura/sfondo.png');
	margin: 0px;
}

#main {
	color: #000000;
	background-color: #FFFFFF;
	height: 100%;
	width: 481px;
	z-index: 1;
	position: absolute;
	top: 435px;
	left: 248px;
}

#menu {
	color: #000000;
	height: 100%;
	width: 172px;
	z-index: 1;
	position: absolute;
	top: 435px;
	left: 55px;
}

#table-menu {
	width: 172px;
	height: 100%;
	border-spacing:0;
	border-collapse:collapse;
}

#test-menu {
	background-image: url('images/struttura/Testata_menu.png');
	height: 19px;
}

#content-menu {
   color: #000000;
	height: 100%;
	background-color: #FFFFFF;
   vertical-align: top;
}

#testata {
	height: 382px;
	width: 652px;
	z-index: 1;
	position: absolute;
	top: 53px;
	left: 157px;
}

#table-testata {
	width: 652px;
	height: 382px;
	border-spacing:0;
	border-collapse:collapse;
}

#test0 {
	background-image: url('images/struttura/Testata_0.jpg');
	height: 83px;
}
#test1 {
	background-image: url('images/struttura/Testata_1.jpg');
	height: 95px;
}
#test2 {
	background-image: url('images/struttura/Testata_2.jpg');
	height: 87px;
}
#test3 {
	background-image: url('images/struttura/Testata_3.jpg');
	height: 117px;
}