Mmmm.. potresti provare con una soluzione javascript:

codice:
<html>
<head>
<title>Test</title>
<script>
function test(){
var s_width ='';
var s_height ='';
s_width=screen.width
s_height=screen.height

if (s_width == "640"){
 document.getElementById("tuodiv").style.display="none";
}

if (s_width == "800"){
 document.getElementById("tuodiv").style.display="none";
}

if (s_width == "1024"){
document.getElementById("tuodiv").style.display="block";
}

if (s_width == "1280"){
 document.getElementById("tuodiv").style.display="block";
} 
}
</script>
</head>

<body onload="test();">
<div id="tuodiv" style="width:200px;height:200px;border:1px solid #000;display:none;"></div>
</body>
</html>