title: Quotes in XML. Single or double?
body: <p>I've heard that using single quotes to surround XML attribute values is a "bad style". Is this correct?</p>
  
  <p>Should I always write:  </p>
  
  <pre><code>&lt;element attr="value"&gt;
  </code></pre>
  
  <p>Or is it acceptable to write:  </p>
  
  <pre><code>&lt;element attr='value'&gt;
  </code></pre>
  
  <p>Or does it not matter which style I use?</p>