The <i>ifdef</i> tag allows for optional processing to occur if a tag is defined. If the tag is undefined, the body of the tag is not processed.<br>

  <pre>
  &lt;i18n:ifdef key="USONLY"&gt;
     Only users specifying en-US as their locale will see this!
  &lt;/i18n:ifdef&gt;
  </pre>
  <i>
  <i18n:ifdef key="USONLY">
     Only users specifying en-US as their locale will see this!
  </i18n:ifdef>
  </i>