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>
    <allfileusages gafcontinue="Balasubramanian.jpg|13239" />
  </query-continue>
  <query>
    <pages>
      <page pageid="128" ns="0" title="Robert Baden-Powell" />
      <page pageid="1288" ns="0" title="Bai Ling" />
      <page pageid="3379" ns="0" title="Bahiyyah Maroon" />
      <page pageid="6891" ns="0" title="Babi Badalov" />
      <page pageid="11096" ns="0" title="Michael McConnell" />
      <page pageid="11098" ns="0" title="Jack Baker" />
      <page pageid="13802" ns="0" title="Babak Erfani" />
      <page pageid="16483" ns="0" title="Oliver Baez Bendorf" />
      <page pageid="17328" ns="0" title="Bajazid Elmaz Doda" />
    </pages>
  </query>
</api>