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="ExportData.png|30" />
  </query-continue>
  <query>
    <pages>
      <page pageid="27" ns="0" title="Open Source GIS Software" />
      <page pageid="30" ns="0" title="Home Range Calculation Manual" />
      <page pageid="65" ns="0" title="About Me" />
      <page pageid="78" ns="0" title="IDE architecture design" />
      <page pageid="90" ns="0" title="Cedeus Evaluacion de GeoNode" />
    </pages>
  </query>
</api>