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')
};