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="Dev6.png|27" />
  </query-continue>
  <query>
    <pages>
      <page pageid="27" ns="0" title="Digital development" />
      <page pageid="39" ns="0" title="How to Take a Three-Colour Image using iTelescope" />
      <page pageid="46" ns="0" title="Get Started with iTelescope" />
      <page pageid="90" ns="0" title="How to Figure Out Which Objects are Visible to Which Telescopes" />
    </pages>
  </query>
</api>