Gastón se hace con javascript, acá te paso para 3 tipos diferentes de resolución.
<html>
<head>
<script LANGUAGE="JavaScript">
function redireccionar() {
var url640x480 = "http://www.tuweb.com/640x480";
var url800x600 = "http://www.tuweb.com/800x600";
var url1024x768 = "http://www.tuweb.com/1024x768";
if ((screen.width == 640) && (screen.height == 480))
window.location.href= url640x480;
else if ((screen.width == 800) && (screen.height == 600))
window.location.href= url800x600;
else if ((screen.width == 1024) && (screen.height == 768))
window.location.href= url1024x768;
else window.location.href= url640x480;
}
</script>
</head>
<body onLoad="redireccionar()">
</body>
</html>
Saludos de alguien que ya conocés
