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>
    <pages>
      <page pageid="21" ns="0" title="Crue de décembre 2008" />
      <page pageid="3" ns="0" title="Crues de l&#039;Eze" />
      <page pageid="10" ns="0" title="Faune" />
      <page pageid="4" ns="0" title="Loi Barnier" />
      <page pageid="2" ns="0" title="Éze" />
    </pages>
  </query>
</api>