ho provato a centrare la pagina e a dare uno sfondo colorato al body per evitare i margini bianchi con risoluzioni maggiori di 1024x768....
prova come va

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>Untitled Document</title>
<style type="text/css">
<!--
html,body{

margin: 0 auto;

padding:0;
text-align:center;
height: 100%;
background-color: #18a441;

}
div#contenitore {
width: 1024px;
height: 100%;
margin: 0 auto;
background: url("img/home.png") no-repeat;
}
div#menuidex {
position:absolute;
width: 1024px;
height: 21px;
top: 170px;
}
img {
border: 0px;
}
a:link {
	color: #CC0000;
	text-decoration: none;
}
a:visited {
	text-decoration: none;
	color: #330000;
}
a:hover {
	text-decoration: none;
	color: #330000;
}
a:active {
	text-decoration: none;
	color: #330000;
}
-->
</style>
<script type="text/javascript">
<!--
function MM_preloadImages() { //v3.0
  var d=document; if(d.images){ if(!d.MM_p) d.MM_p=new Array();
    var i,j=d.MM_p.length,a=MM_preloadImages.arguments; for(i=0; i<a.length; i++)
    if (a[i].indexOf("#")!=0){ d.MM_p[j]=new Image; d.MM_p[j++].src=a[i];}}
}
function MM_swapImgRestore() { //v3.0
  var i,x,a=document.MM_sr; for(i=0;a&&i<a.length&&(x=a[i])&&x.oSrc;i++) x.src=x.oSrc;
}
function MM_findObj(n, d) { //v4.01
  var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
    d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}
  if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
  for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers[i].document);
  if(!x && d.getElementById) x=d.getElementById(n); return x;
}

function MM_swapImage() { //v3.0
  var i,j=0,x,a=MM_swapImage.arguments; document.MM_sr=new Array; for(i=0;i<(a.length-2);i+=3)
   if ((x=MM_findObj(a[i]))!=null){document.MM_sr[j++]=x; if(!x.oSrc) x.oSrc=x.src; x.src=a[i+2];}
}
//-->
</script>
</head>
<body onload="MM_preloadImages('img/rolloverhomebutton.gif','img/rolloverprogrammabutton.gif','img/rolloverluoghibutton.gif','img/rollovercontattibutton.gif')">
<div id="contenitore">
<div id="menuidex">
[img]img/homebutton.gif[/img][img]img/programmabutton.gif[/img][img]img/luoghibutton.gif[/img][img]img/contattibutton.gif[/img]
</div>
</div>
</body>
</html>