title: Non-Standard Attributes on HTML Tags. Good Thing? Bad Thing? Your Thoughts?
body: <p>HTML (or maybe just XHTML?) is relatively strict when it comes to non-standard attributes on tags. If they aren't part of the spec, then your code is considered non-compliant.</p>
  
  <p>Non-standard attributes can be fairly useful for passing along meta-data to Javascript however. For instance, if a link is suppose to show a popup, you can set the name of the popup in an attribute:</p>
  
  <pre><code>&lt;a href="#null" class="popup" title="See the Popup!" 
     popup_title="Title for My Popup"&gt;click me&lt;/a&gt;
  </code></pre>
  
  <p>Alternatively, you can store the title for the popup in a hidden element, like a span:</p>
  
  <pre><code>&lt;style&gt;
      .popup .title { display: none; }
  &lt;/style&gt;
  &lt;a href="#null" title="See the Popup!" class="popup"&gt;
      click me
      &lt;span class="title"&gt;Title for My Popup&lt;/span&gt;
  &lt;/a&gt;
  </code></pre>
  
  <p>I am torn however as to which should be a preferred method. The first method is more concise and, I'm guessing, doesn't screw with search engines and screen readers as much. Conversely, the second option makes storing large amounts of data easier and is thus, more versatile. It is also standards compliant.</p>
  
  <p>I am curious what this communities thoughts are. How do you handle a situation like this? Does the simplicity of the first method outweigh the potential downsides (if there are any)?</p>