var WinPC  = ((navigator.appVersion.indexOf("Win")!=-1) || 
              (navigator.appVersion.indexOf("win")!=-1) || 
              (navigator.appVersion.indexOf("WIN")!=-1));
var IE     = (navigator.appName.indexOf("Microsoft") != -1);
var NC     = (navigator.appName.indexOf("Netscape") != -1);
var V40    = (navigator.appVersion.charAt(0) >= 4);
var V50    = (navigator.appVersion.indexOf("5.") != -1);
W3C = ((!IE) && (V50));

if (screen.height<500) _screen = 1; //640x480
else if (screen.height<650) _screen = 2;
else if (screen.height<800) _screen = 3;
else _screen = 4;