... solo un esempio,
ma se fai tutto con file esterni è meglio
http://css.html.it/
codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>

<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>Titolo pagina</title>
<style type="text/css">
#miatabella {background: blue; width:100%; border:3px solid #000;}
</style>
</head>

<body>
<table id="miatabella" cellpadding="1px" cellspacing="0px">
	<tr>
		<td>
		</td>
	</tr>
</table>
</body>

</html>
ciao