title: Is it acceptable to use single quotes around values in HTML attributes?
body: <p>Is it acceptable to use single quotes around html attribute values like this:</p>
  
  <pre><code>&lt;span class='classname'&gt;Hi&lt;/span&gt;
  </code></pre>
  
  <p>Instead of double quotes like this:</p>
  
  <pre><code>&lt;span class="classname"&gt;Hi&lt;/span&gt;
  </code></pre>
  
  <p>Who defines what's okay? W3C?</p>