You can pass JavaScript results to ASP server side page with some simple form like:
<html>
<body>
<form target="set_resolution.asp" method="post" id="frm_scr" name="frm_scr">
<input type="hidden" id="scr_width" value="">
<input type="hidden" id="scr_height" value="">
</form>
<script>
document.getElementById(scr_width'').value=document.body.clientWidth;
document.getElementById('scr_height').value=document.body.clientHeight;
document.getElementById('frm_scr').submit();
</script>
</body>
<html>
====================
be note that document.body.clientHeight/Width is available in IE 8+. There is other way to get screen dimensions with JavaScript, but the idea to pass that data to ASP is same. Hope that this help