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="BLi_OOo_1024x768.jpg|21650" />
  </query-continue>
  <query>
    <pages>
      <page pageid="13599" ns="0" title="OOoES/Traduccion/Calc: Funciones Bases de Datos" />
      <page pageid="13942" ns="2" title="User:Stefanw/Anwenderfrühstück" />
      <page pageid="14118" ns="2" title="User:Stefanw/Linuxwochen Wien 2008" />
      <page pageid="16861" ns="2" title="User:Arielch/Menu API Enhancement" />
      <page pageid="17888" ns="0" title="Art/Gallery" />
      <page pageid="24367" ns="0" title="Education Project/Effort/Various adaptations on Sugar/Work In Progress" />
    </pages>
  </query>
</api>