title: Adding data to XHTML tags
body: <p>My website is XHTML 1.1, and I had added 'rel' attributes to the <code>&lt;li&gt;</code> and <code>&lt;div&gt;</code> tags on my page, to store data for a jQuery script on the page.  When validating my page, I get the error: "there is no attribute 'rel'".  So, what is the best way to store arbitrary data in HTML tags?</p>
  
  <p>I am working on a comments page for my website.  When a comment is entered, it is POSTed via AJAX, which returns JSON of all comments.  I then look at the 'rel' values to see which comments are already on the page, and only add the new ones.</p>
  
  <p>The jQuery code works fine, it's just the 'rel' attributes don't validate.</p>