You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <alltransclusions gatcontinue="Box_portal_skeleton/Selected_biography/5" />
  </query-continue>
  <query>
    <pages>
      <page ns="10" title="Template:Box portal skeleton/Categories" missing="" />
      <page ns="10" title="Template:Box portal skeleton/Did you know" missing="" />
      <page ns="10" title="Template:Box portal skeleton/Intro" missing="" />
      <page ns="10" title="Template:Box portal skeleton/News" missing="" />
      <page ns="10" title="Template:Box portal skeleton/Opentask" missing="" />
      <page ns="10" title="Template:Box portal skeleton/Projects" missing="" />
      <page ns="10" title="Template:Box portal skeleton/Related portals" missing="" />
      <page ns="10" title="Template:Box portal skeleton/Selected article/5" missing="" />
      <page pageid="9" ns="10" title="Template:Box-footer" />
      <page pageid="10" ns="10" title="Template:Box-header" />
    </pages>
  </query>
</api>