function cwindowV(w_height) {
  var sHeight = screen.availHeight;
  var cHeight = sHeight/2;
  var vpos;

   if(w_height<sHeight) vpos = cHeight-(w_height/2);
    else vpos=0;
  
   return vpos; 

}

function cwindowH(w_width) {
  var sWidth=screen.availWidth;
  var cWidth=sWidth/2;
  var hpos;

  if(w_width<sWidth)hpos=cWidth-(w_width/2);   
    else hpos = 0;
  
  return hpos;

}