prova cosi':
codice:
<style type="text/css">
<!--
#xxx {
	width: 100%;
}#xxx .td1 {
	width: 50%;
	background-color:#00CCFF;
}
#xxx .td2 {
	width: 40%;
	background-color:#FFFF99;
}
#xxx .td3 {
	width: 10%;
	background-color:#CCCCFF;
}
-->
</style>
</head>

<body>

<table id="xxx">
		<thead>
			   <tr>
				   <th class="td1">1</th>
				   <th class="td2">2</th>
				   <th class="td3">3</th>
			   </tr>
		</thead>
...
ciak