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 afcontinue="LostMine_pic6.jpg|95" />
  </query-continue>
  <query>
    <allfileusages>
      <f ns="6" title="File:BlackSpider note1.jpg" />
      <f ns="6" title="File:BlackSpider note2.jpg" />
      <f ns="6" title="File:Cragmaw note.jpg" />
      <f ns="6" title="File:ListOfTheGods.jpg" />
      <f ns="6" title="File:LostMine pic1.jpg" />
      <f ns="6" title="File:LostMine pic10.jpg" />
      <f ns="6" title="File:LostMine pic2.jpg" />
      <f ns="6" title="File:LostMine pic3.jpg" />
      <f ns="6" title="File:LostMine pic4.jpg" />
      <f ns="6" title="File:LostMine pic5.jpg" />
    </allfileusages>
  </query>
</api>