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="GimpImage.png|121" />
  </query-continue>
  <query>
    <pages>
      <page pageid="72" ns="0" title="Mindstorm:n-point image deformation tool" />
      <page pageid="110" ns="0" title="Hacking:GIMPCon 2004, Kristiansand, Norway, 2004" />
      <page pageid="121" ns="0" title="Hacking:How to write a GIMP plug-in" />
      <page pageid="133" ns="0" title="Screenshots of the development version" />
      <page pageid="175" ns="0" title="Flood algorithm" />
    </pages>
  </query>
</api>