Scroll based navigation bar (inspired by Teehan+Lax)

scrollBasedNavBar.js

var lastScrollY = 0,
minScroll = 20,
delay = 150;

var navMovement = setInterval(function() {
  var nav = document.getElementById('nav')
  var scrollY = document.all? iebody.scrollTop : pageYOffset;
  if(scrollY + minScroll < lastScrollY || scrollY <= 25) {
    nav.style.top = "0px"
  } else if (scrollY > lastScrollY){
    nav.style.top = - nav.offsetHeight + "px"
  }
  lastScrollY = scrollY;
}, delay);