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="Calendar-jour-futur-mois-affiche.gif|2224" />
  </query-continue>
  <query>
    <pages>
      <page pageid="980" ns="0" title="Rapporter un bug" />
      <page pageid="2224" ns="0" title="Calendrier" />
      <page pageid="2252" ns="0" title="Installation armoire à clés" />
      <page pageid="2542" ns="0" title="Gestion des budgets" />
      <page pageid="2604" ns="0" title="Panier de réservation" />
      <page pageid="2630" ns="0" title="Tableurs" />
      <page pageid="2727" ns="0" title="Interfaçage OpenFlyers et Charterware" />
    </pages>
  </query>
</api>