var l=screen.width;
switch(l) {
 case 800:
  document.write("<link rel='stylesheet' href='VRB.css' type='text/css'>");
 break;
 case 1280:
  document.write("<link rel='stylesheet' href='VRA.css' type='text/css'>");
 break;
 default:
  document.write("<link rel='stylesheet' href='VR.css' type='text/css'>");
}