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="Bong.jpg" />
  </query-continue>
  <query>
    <pages>
      <page ns="6" title="File:Barbara Lee.jpg" missing="" />
      <page ns="6" title="File:Barney Frank.jpg" missing="" />
      <page ns="6" title="File:Bhangshop.jpg" missing="" />
      <page ns="6" title="File:BillMaherSept10.jpg" missing="" />
      <page ns="6" title="File:Bill Clinton.jpg" missing="" />
      <page ns="6" title="File:Blackberry medical cannabis.jpg" missing="" />
      <page ns="6" title="File:BlueRhino.JPG" missing="" />
      <page ns="6" title="File:Blueberry (Dutch Passion) 02.jpg" missing="" />
      <page ns="6" title="File:Bluedream.jpg" missing="" />
      <page ns="6" title="File:Bob-Marley.jpg" missing="" />
    </pages>
  </query>
</api>