function PopUp (URL, X, Y, W, H, settings)
   {
   var myBrowser = navigator.appName;
   if (X ==  0) {X = (screen.availWidth-W)/2;}
   if (X == -1) {X =  0;}
   if (X == -2) {X =  screen.availWidth-W;}
   if (Y ==  0) {Y = (screen.availHeight-H)/2;}
   if (Y == -1) {Y =  0;}
   if (Y == -2) {Y =  screen.availHeight-H;}
   if (W ==  0) {W =  screen.availWidth-10;  X = 0;}
                           // Full screen puts popup under calling page.
   if (H ==  0) {H =  screen.availHeight-10; Y = 0;}

   settings = settings + ', height=' + H + ', width=' + W;

   // Internet explorer.
   if (myBrowser == 'Microsoft Internet Explorer')
      {settings = settings + ', top=' + Y + ', left=' + X;}

   // Netscape.
   if (myBrowser == 'Netscape')
      {settings = settings + ', screenX=' + X + ', screenY=' + Y;}

   var w=window.open (URL, '', settings, true);
   }