var backgroundset=false;   // do not change, for internal use only

  function fixedBackground(url)
  {
    if(!backgroundset)
    {
      document.body.style.overflow = 'hidden';
      document.body.style.padding  = '0px';
      document.body.style.margin   = '0px';

      var overlay = document.createElement('DIV');
      overlay.style.position    = 'absolute';
      overlay.style.top         = '0px';
      overlay.style.left        = '0px';
      overlay.style.height      = '100%';
      overlay.style.width       = '100%';
      overlay.style.overflow    = 'auto';

      overlay.innerHTML         = document.body.innerHTML;
      document.body.innerHTML   = '<img id="background" height="100%"  width="100%" src="' + url + '" style="left: 0; bottom: 0; right: 0; top: 0; z-index: 0" />';

      document.body.appendChild(overlay);

      backgroundset=true;
    }
    else
      background.src=url;
  }