Questo il codice rivisto e semplificato (solo relativamente al div con le foglie, per gli altri sarebbero da evitare i posizionamenti assoluti e se devi avere div affiancati ricorrere ai float)
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>melameno.me - cercasi webmaster </title>
<style type="text/css">
<!--
#sfondo {
position: relative;
width:474px;
height:474px;
background:url(img/home/foglie2.png) no-repeat;
}
#sfondo img {
vertical-align:bottom;
border:0;
}
a#topsx, a#topdx, a#downsx, a#downdx {
position: absolute;
display:block;
width:237px;
height:237px;
opacity:1;
}
a#topsx:hover, a#topdx:hover, a#downsx:hover, a#downdx:hover {
opacity:0;
}
a#topsx {
top: 0;
left: 0;
}
a#topdx {
top: 0;
right: 0;
}
a#downsx {
bottom: 0;
left: 0;
}
a#downdx {
bottom: 0;
right: 0;
}
a#centro {
position: absolute;
display:block;
width:144px;
height:144px;
top: 164px;
left: 165px;
z-index: 6;
background:url(img/home/centro2.png) no-repeat;
opacity:1;
}
a#centro img {
padding-top:14px;
padding-left:13px;
opacity:0;
}
a#centro:hover img {
opacity:1;
}
-->
</style>
<!--[if lte IE 8]>
<style type="text/css">
* {zoom:1}
a#topsx:hover, a#topdx:hover, a#downsx:hover, a#downdx:hover {
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=100)";
filter: alpha(opacity=100);
}
a#topsx:hover, a#topdx:hover, a#downsx:hover, a#downdx:hover {
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=0)";
filter: alpha(opacity=0);
}
a#centro img{
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=0)";
filter: alpha(opacity=0);
}
a#centro:hover img{
-ms-filter: "progid:DXImageTransform.Microsoft.Alpha(Opacity=100)";
filter: alpha(opacity=100);
}
</style>
<![endif]-->
</head>
<body>
<div id="sfondo">
[img]img/home/1.jpg[/img]
[img]img/home/2.jpg[/img]
[img]img/home/3.jpg[/img]
[img]img/home/4.jpg[/img]
[img]img/home/progetti2.png[/img]
</div>
</body>
</html>
edit
osps, dovevo postarlo nell'altra discussione, vabbè, è uguale