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="Capoferro-Plate-7.jpg|113" />
  </query-continue>
  <query>
    <pages>
      <page pageid="108" ns="0" title="Ridolfo Capoferro" />
      <page pageid="113" ns="0" title="Capoferro Plate 7" />
      <page pageid="117" ns="0" title="Capoferro Plate 10" />
      <page pageid="121" ns="0" title="Capoferro Plate 11" />
      <page pageid="124" ns="0" title="Capoferro Plate 12" />
      <page pageid="125" ns="0" title="Capoferro Plate 13" />
    </pages>
  </query>
</api>