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="BEL_Leg2.png|6305" />
  </query-continue>
  <query>
    <pages>
      <page pageid="2550" ns="0" title="Semi-Condominium de Freineubourg" />
      <page pageid="3214" ns="0" title="Université Fédérale Scanthéloise" />
      <page pageid="3441" ns="0" title="Association des Transporteurs Aériens de l&#039;Archipel" />
      <page pageid="6058" ns="0" title="Aérodrome national de Bergenberg" />
      <page pageid="6147" ns="0" title="Centre Micromondial de Logotypes" />
      <page pageid="6305" ns="0" title="Belgoge" />
      <page pageid="7922" ns="0" title="1e Salon Micromondial de l&#039;Aéronautique" />
      <page pageid="7924" ns="0" title="2e Salon Micromondial de l&#039;Aéronautique" />
      <page pageid="8807" ns="0" title="3e Salon Micromondial de l&#039;Aéronautique" />
    </pages>
  </query>
</api>