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="Kurs10.png" />
  </query-continue>
  <query>
    <pages>
      <page ns="6" title="Fil:Dialog-warning.svg" missing="" />
      <page ns="6" title="Fil:Edit-copy green.svg" missing="" />
      <page ns="6" title="Fil:Imbox content.png" missing="" />
      <page ns="6" title="Fil:Imbox notice.png" missing="" />
      <page ns="6" title="Fil:Increase2.svg" missing="" />
      <page pageid="181" ns="6" title="Fil:BKB logo.png" />
      <page pageid="46" ns="6" title="Fil:Crystal Clear action configure.png" />
      <page pageid="51" ns="6" title="Fil:Eksempel.jpg" />
      <page pageid="229" ns="6" title="Fil:Felixsnus.jpg" />
      <page pageid="294" ns="6" title="Fil:Kurs1.png" />
    </pages>
  </query>
</api>