title: What are legal characters for an HTML element id?
body: <p>What characters can I use in an identifier for an HTML element?  </p>
  
  <p>For example:</p>
  
  <p><code>&lt;SPAN id="section[5]" ...&gt;</code></p>
  
  <p>(Or rather, should I stick to certain characters to make sure the <code>id</code> works across all major browsers/JavaScript engine). </p>