function showPopupWindow(url, name, width, height)
{
   var xpos = (screen.width-width) / 2;
   var ypos = (screen.height-height) / 2;
   var features = 'toolbar=0,scrollbars=1,location=0,statusbar=0,menubar=0,resizable=1';
   features += ',width=';
   features += width;
   features += ',height=';
   features += height;
   features += ',left=';
   features += xpos;
   features +=',top=';
   features += ypos;

   popupWin = window.open(url, name, features);
   popupWin.focus();
}