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="Cond-10.jpg|11" />
  </query-continue>
  <query>
    <pages>
      <page pageid="135" ns="0" title="Manual Express" />
      <page pageid="251" ns="0" title="Manual Express v3" />
      <page pageid="322" ns="0" title="Troubleshooting Vixen" />
      <page pageid="350" ns="0" title="Manual Express v4" />
      <page pageid="357" ns="0" title="Bare bones PIC18F programmer interface" />
      <page pageid="650" ns="0" title="Manual Tester" />
      <page pageid="651" ns="0" title="Manual Servo" />
      <page pageid="758" ns="0" title="Manual Conductor" />
      <page pageid="872" ns="0" title="Manual Slave" />
    </pages>
  </query>
</api>