function redrawBg()
  {
    $('page-left-shadow').addClassName('page-left-shadow');
    $('page-right-shadow').addClassName('page-right-shadow');
    
    var dim = $('page').getDimensions();
    var scr = document.viewport.getDimensions();
    var maxY = Math.max(dim.height,scr.height);
    $$('.top-shadow,.bottom-shadow').invoke('setStyle','height: '+((maxY - 749)/2)+'px;');
    var shadowWidth = (document.viewport.getDimensions().width - dim.width)/2;
    if (shadowWidth < 0)
      shadowWidth = 0;
    $$('.page-left-shadow div,.page-right-shadow div,.page-left-shadow,.page-right-shadow').invoke('setStyle','width: '+shadowWidth+'px;');
    $$('.page-left-shadow').invoke('setStyle','background-position: 0; margin-left: -'+((dim.width/2) + shadowWidth)+'px;');
    $$('.page-right-shadow').invoke('setStyle','background-position: 0; margin-right: -'+((dim.width/2) + shadowWidth)+'px;');
  }

Event.observe(window, 'load', function() 
{
  redrawBg();
});