You have several issues :
First: you should write your code like that :
$(function () {
//your code here
});
It will fire your code only when jQuery is ready.
Secondly, in your case inside your jsfiddle, fancybox lib isn't loaded.
you should add that:
<link type="text/css" rel="stylesheet" href="//cdn.jsdelivr.net/fancybox/2.1.5/helpers/jquery.fancybox-buttons.css" />
<script type="text/javascript" src="//cdn.jsdelivr.net/fancybox/2.1.5/helpers/jquery.fancybox-buttons.js"></script>
<script type="text/javascript" src="//cdn.jsdelivr.net/fancybox/2.1.5/helpers/jquery.fancybox-media.js"></script>
<link type="text/css" rel="stylesheet" href="//cdn.jsdelivr.net/fancybox/2.1.5/helpers/jquery.fancybox-thumbs.css" />
<script type="text/javascript" src="//cdn.jsdelivr.net/fancybox/2.1.5/helpers/jquery.fancybox-thumbs.js"></script>
<link type="text/css" rel="stylesheet" href="//cdn.jsdelivr.net/fancybox/2.1.5/jquery.fancybox.css" />
<script type="text/javascript" src="//cdn.jsdelivr.net/fancybox/2.1.5/jquery.fancybox.js"></script>
<script type="text/javascript" src="//cdn.jsdelivr.net/fancybox/2.1.5/jquery.fancybox.pack.js"></script>
Then finally, your url must be a picture:
Like that:
<span class="test" url="http://farm3.static.flickr.com/2647/3867677191_04d8d52b1a.jpg">It's a test</span>
Here the jsfiddle : http://jsfiddle.net/5QYGe/1/