$(function() {
  var rotation = 0, 
    scrollLoc = $(document).scrollTop();
  
  $(window).scroll(function() {
    var newLoc = $(document).scrollTop();
    
    var diff = scrollLoc - newLoc;
    rotation -= diff, scrollLoc = newLoc;
    
    var rotationStr = "rotate(" + rotation/10 + "deg)";
    var skewStr = "skew(" + rotation/90 + "deg)";
    var opacityStr = "0." + Math.round( rotation/100);
    $(".rotate").css({
      "-webkit-transform":  rotationStr + skewStr,
      "-moz-transform": rotationStr + skewStr,
      "transform":   rotationStr + skewStr,
      "opacity": opacityStr
    });
  });
})