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="Backtosquareone.jpg|522" />
  </query-continue>
  <query>
    <pages>
      <page pageid="3418" ns="0" title="Backs to the Wall" />
      <page pageid="3473" ns="0" title="Backfire" />
      <page pageid="6607" ns="0" title="Spell Shattering Arrow" />
      <page pageid="7779" ns="0" title="Malevolent Mech - Goku En" />
      <page pageid="7781" ns="0" title="Paladin of the Cursed Dragon" />
      <page pageid="7783" ns="0" title="Zombie World" />
      <page pageid="7785" ns="0" title="Imperial Iron Wall" />
      <page pageid="8057" ns="0" title="B. Skull Dragon" />
      <page pageid="8109" ns="0" title="Baby Dragon" />
      <page pageid="9859" ns="0" title="B.E.S. Big Core MK-2" />
    </pages>
  </query>
</api>