function popup_ad(x,y) {
       var posCode = '';
       var minWidth=x;
       var minHeight=y;
       if (document.all || document.layers || document.createTextNode) {
        posX = Math.round((screen.width - minWidth) / 2);
        posY = Math.round((screen.height - minHeight) / 2);
        posCode = (document.all)? 'left='+posX+',top='+posY : 'screenX='+posX+',screenY='+posY;
       }
       cardWindow = window.open('popup.ad.php?sizeX=' + minWidth + '&sizeY=' + minHeight,'','menubar=no,toolbar=no,scrollbars=no,status=no,width='+minWidth+',height='+minHeight+','+posCode);
      }