title: $(this) children always returns undefined
body: <p>I have problem with <code>undefined</code> being returned by <code>innerHTML</code>. Maybe it is because of a difference between <code>html()</code> and <code>innerHTML</code>?</p>
  
  <p>My JavaScript code:</p>
  
  <pre><code>var content2 = document.getElementById("content2");
  var opis;
  
  $(function() {
    $('.blok').click(function(e) {
      opis = $(this).next('.opis');
      if (!$('.popup:visible').length) {
          content2.innerHTML= opis.html();
          $('.popup').fadeIn();
      }
      e.preventDefault();
      return false;
    });
  
    $('.popup .close, .popup .bg').click(function() {
      $(this).parents('.popup').fadeOut();
    });
  })
  </code></pre>
  
  <p>My HTML:</p>
  
  <pre><code>&lt;body oncontextmenu="return false" onselectstart="return false" onselect="return false" oncopy="return false"&gt;
      &lt;div class="popup"&gt; 
          &lt;div class="bg"&gt;&lt;/div&gt; 
          &lt;div class="container"&gt; 
              &lt;div id="content2"&gt; &lt;/div&gt; 
          &lt;/div&gt; 
      &lt;/div&gt; 
      And example of "blok": 
      &lt;div class="blok"&gt; $$|DO| = |OC| = 5$$ &lt;div class="opis"&gt;2&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Why does content2 always return <code>undefined</code>?</p>