$(document).ready(function(){
 var skyscraperAd = $("#menu");
 var skyscraperOffset = skyscraperAd.offset().top;
 var skyscraperBottom = $("#foot").offset().top - skyscraperAd.height();
 $(window).scroll(function() {
   skyscraperAd.stop();
   var windowTop = $(window).scrollTop();
   if (windowTop > skyscraperOffset) {
      if (windowTop > skyscraperBottom) windowTop = skyscraperBottom;
      if (windowTop < 0) windowTop = 0;
      skyscraperAd.animate({top: windowTop + 'px'}, 'fast');
   } else
      skyscraperAd.animate({top: skyscraperOffset + 'px'},'fast');
 });
});