title: What is a good definition for language code and locale codes?
body: <p><li>When to use <code>en_GB</code> and <code>en-GB</code> ?
  <li>What is the difference ?
  <li>Is there an ISO name for this <code>ISO 639-1</code> (language) and <code>ISO 3166</code> (country) combination ?</p>