title: popup displaying partly outside browser window
body: <p>I am using CSS to create a pop-up on my page. I have a  within the  tag that is set to display:none;. Then when you hover over the  tag the definition of the word pops up. This is working wonderful for me, HOWEVER sometimes the pop-up is appearing outside the browser window. Is there a way to make sure that the entire pop-up stays within the browser window with CSS or so I need to add in some Javascript? I would really like the pop-up to appear at the location of the link but I don't care if it moves left or right in order to be within the window and visible.</p>
  
  <p>This is my code:</p>
  
  <pre><code>a span {
  display: none;
  }
  
  a:hover span {
  display: block;
  position: absolute;
  width: 300px;
  z-index: 1000;
  }
  </code></pre>
  
  <p>Thank you in advance for your help! :-)</p>