function openwindow(url,w,h)  {
  var winwidth = screen.availWidth;
  var winheight = screen.availHeight;
  var leftt=Math.floor((winwidth/2)-(w/2));
  var topt=Math.floor((winheight/2)-(h/2));
  window.open(url,'popup','left='+leftt+',top='+topt+',width='+w+',height='+h+',toolbar=0,location=0,directories=0,status=0,titlebar=0,menubar=0,resizable=1,scrollbars=1');
}