title: Showing div on scroll just once
body: <p>Just like the title says! I'm having this div appear on scroll and I have the code, but I want the action to occur only once. And not happen again if I decide to close the div(it's an alert) and scroll down again. How can I achieve this? </p>
  
  <p>I've read everything I could find, but since I'm a newbie, it was all too confusing for me to understand.</p>
  
  <p>Anyway, here's my code so far:</p>
  
  <pre><code>$(document).scroll(function () {
      var y = $(this).scrollTop();
      if (y &gt; 100) {
          $('#alert').fadeIn();
      } 
  });
  </code></pre>
  
  <p>What do I need to add to this? 
  Thank you!</p>