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="Exchhost2013_multisendcon_newaccount_step_1.png|23" />
  </query-continue>
  <query>
    <pages>
      <page pageid="12" ns="0" title="Créer un serveur openVPN avec ipFire" />
      <page pageid="23" ns="0" title="Exchange Hosted 2013 : Créer un nouveau compte" />
    </pages>
  </query>
</api>