XML elements can't overlap. Here's some markup that isn't legal:

<!-- NOT legal XML markup -->            
<p>
  <b>I <i>really 
  love</b> XML.
  </i>
</p>
          

If you begin a <i> element inside a <b> element, you have to end it there as well. If you want the text XML to appear in italics, you need to add a second <i> element to correct the markup:

<!-- legal XML markup -->
<p>
  <b>I <i>really 
  love</i></b>
  <i>XML.</i>
</p>
          

An XML parser will accept only this markup; the HTML parsers in most Web browsers will accept both.