You can do it by using JavaScript.
The following function redirects to a new page according to the client's resolution.
<script language="JavaScript">
function resolutionRedirect(){
if (screen.width == 640){
window.location.href= "http://www.mysite.com/small.html";
}
else if (screen.width == 800){
window.location.href= "http://www.mysite.com/medium.html";
}
else if (screen.width == 1024){
window.location.href= "http://www.mysite.com/big.html";
}
else {
window.location.href= "http://www.mysite.com/others.html";
}
}
</script>
<body onLoad="resolutionRedirect();">
Play with different values according to today's most common screen resolutions.
REGARDS