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="Curious.PNG|21" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page" />
      <page pageid="22" ns="0" title="Crushbone" />
      <page pageid="48" ns="0" title="City of Mist" />
      <page pageid="68" ns="0" title="Main-Test" />
      <page pageid="72" ns="0" title="Improved Charm Quest" />
      <page pageid="77" ns="0" title="Chaotic Armor Quest" />
      <page pageid="99" ns="0" title="World Bosses" />
      <page pageid="110" ns="0" title="Turg the Thief" />
      <page pageid="251" ns="0" title="Zone Chart" />
    </pages>
  </query>
</api>