title: Correct html5 boolean attribute syntax?
body: <p>What is the correct (or suggested) syntax for boolean html attributes? For example which one of the following should I use?</p>
  
  <pre><code>&lt;input type="text" disabled&gt;
  &lt;input type="text" disabled="disabled"&gt;
  &lt;input type="text" disabled="true"&gt;
  </code></pre>