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="S_MBoard_v11.jpg|1408" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1408" ns="0" title="Hardware" />
      <page pageid="1409" ns="0" title="Scripting commands and tools" />
      <page pageid="1410" ns="0" title="IP block desing" />
      <page pageid="1427" ns="0" title="Examples and reference designs" />
      <page pageid="1438" ns="0" title="Main page" />
      <page pageid="1453" ns="0" title="Cyclone 5" />
      <page pageid="1474" ns="0" title="Cyclone III v2.4" />
    </pages>
  </query>
</api>