How about using javascript to detect the screen resolution,
and redirecting the user to the appropriate page if it is below 640
x 480 or so???
Here is a sample script that I came across that you should be
able to modify to suit your needs:
<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
function redirectPage() {
var url640x480 = "
http://www.yoursite.com/640x480";
var url800x600 = "
http://www.yoursite.com/800x600";
var url1024x768 = "
http://www.yoursite.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;
}
// End -->
</SCRIPT>