A CodePen by Chris Williams. Sticky Div - Basic example how to make a div stick to the tippy top of a page by scrolling. Uses jQuery

index.haml

%header
  %h1 Say “hello” to my sticky div!

#stickySpace
  #sticky
    “Hello.”

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script.js

var scrollPos, stick, stickyDiv, stickyDivOffset, stickyState, unstick;

scrollPos = 0;

stickyDiv = $("#sticky");

stickyDivOffset = stickyDiv.offset();

stickyState = "unstuck";

$(document).on("scroll", function() {
  scrollPos = $(this).scrollTop();
  if (scrollPos >= stickyDivOffset.top) {
    stick();
  } else {
    unstick();
  }
  return stickyDiv.text(scrollPos);
});

stick = function() {
  if (stickyState === "unstuck") {
    stickyDiv.addClass("stick");
    return stickyState = "stuck";
  }
};

unstick = function() {
  if (stickyState === "stuck") {
    stickyDiv.removeClass("stick");
    return stickyState = "unstuck";
  }
};

style.scss

@import "compass";
body {
  font-family: sans-serif;
  margin: 0;
  text-align: center;
  background: #333 url(/images/classy_fabric.png);
  color: white;
  font-family: "Lucida Grande", "Lucida Sans Unicode", Tahoma, Sans-Serif;
  header {
    margin: 5em 0;
  }
  
  #stickySpace {
    height: 120px;
  }
  
  #sticky {
    position: static;
    background: #000000;
    height: 60px;
    line-height: 60px;
    width: 50%;
    margin: 0 auto;
    
    &.stick {
      position: fixed;
      top: 0;
      left: 50%;
      margin-left: -25%;
    }
  }
}