title: Bootstrap Affix "Back to Top" Link
body: <p>Alright, I'm having trouble understanding the <a href="http://getbootstrap.com/javascript/#affix" rel="noreferrer">Bootstrap Affix component</a>. My goal is to have a "Back to Top" link appear at the bottom left of the screen (in the margin) if/when the page is scrolled below the top of the content. My page has a NavBar fixed to the top and a container for the body. Below is the general idea of where I'm at but I've also <a href="http://jsfiddle.net/Panman8201/MKZrm/1/" rel="noreferrer">setup a JS Fiddle</a> that demonstrates my setup. I'm also not a pro at positioning so that is part of my issue too.</p>
  
  <pre><code>&lt;div class="navbar navbar-fixed-top"&gt;...&lt;/div&gt;
  &lt;div class="content-container" id="top"&gt;
      &lt;p&gt;Content that is longer than the viewport..&lt;/p&gt;
      &lt;span id="top-link" data-spy="affix"&gt;
          &lt;a href="#top" class="well well-sm"&gt;Back to Top&lt;/a&gt;
      &lt;/span&gt;
  &lt;/div&gt;
  
  &lt;style&gt;
      .navbar-fixed-top + .content-container {
          margin-top: 70px;
      }
      .content-container {
          margin: 0 125px;
      }
      #top-link.affix {
          position: absolute;
          bottom: 10px;
          left: 10px;
      }
  &lt;/style&gt;
  </code></pre>