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="Logo.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="37" ns="6" title="File:Capture bibella.png" />
      <page pageid="23" ns="6" title="File:Coverflow-1.png" />
      <page pageid="34" ns="6" title="File:Drawing toolbar.png" />
      <page pageid="31" ns="6" title="File:Ecran2.png" />
      <page pageid="9" ns="6" title="File:File dezipped.png" />
      <page pageid="33" ns="6" title="File:Horizontal toolbar.png" />
      <page pageid="40" ns="6" title="File:Howto1 step1.jpg" />
      <page pageid="42" ns="6" title="File:Howto1 step3.jpg" />
      <page pageid="43" ns="6" title="File:Howto1 step4.jpg" />
      <page pageid="46" ns="6" title="File:Import symbols.png" />
    </pages>
  </query>
</api>