title: lightbox2 doesn't open image in lightbox
body: <p>I try to integrate Lightbox2 in an existing website.</p>
  
  <p>Head Code:</p>
  
  <pre><code>&lt;head&gt;
   &lt;link rel="stylesheet" media="screen" type="text/css" href="/css/style.css"&gt;
   &lt;link rel="stylesheet" type="text/css" href="/css/lightbox.css"&gt;
  
   &lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.4/jquery.min.js"&gt;&lt;/script&gt;
   &lt;script type="text/javascript" src="/js/lightbox.js"&gt;
  &lt;/head&gt;
  </code></pre>
  
  <p>Image Code:</p>
  
  <pre><code>&lt;div class="image-wrapper"&gt;     
   &lt;a href="/img/projects/folder/image_big.jpg" data-lightbox="lightboxImage"&gt;
    &lt;img src="/img/projects/folder/image_thumbnail.jpg" alt=" " class="project-image"&gt;
   &lt;/a&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>My problem is when I click the thumbnail it only opens the big image in a blank browser window instead of opening it in a lightbox.</p>
  
  <p>I already checked the paths. And the browser console shows no errors.</p>
  
  <p>I think I just missed something. But I don't know what it could be.</p>
  
  <p>Would appreciate some help. Thank you!</p>