title: HTML 5 classnames and IDs
body: <p>I know that in HTML4 classes and id cannot start with numbers.</p>
  
  <p>I am coding in HTML 5/php and alot of my ids and classes have just numbers in them that point to a primary key in my database for jquery ajax calls. </p>
  
  <p>I cannot find the documentation for HTML5 classes and id spec. Is it valid in HTML 5 to have class and id names such as,</p>
  
  <pre><code>class="122"
  id="13213"
  </code></pre>
  
  <p>I have ran my output code through w3c conformance checker and all is good, but still I would like confirmation!?</p>
  
  <p>Thanks</p>