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>
    <alllinks galcontinue="Bloqueo_administrativo_de_períodos" />
  </query-continue>
  <query>
    <pages>
      <page ns="0" title="Balance" missing="" />
      <page ns="0" title="Balance (simple)" missing="" />
      <page ns="0" title="Banco" missing="" />
      <page ns="0" title="Bloque contable" missing="" />
      <page ns="0" title="Bloqueo administrativo" missing="" />
      <page pageid="496" ns="0" title="Bancos" />
      <page pageid="203" ns="0" title="Barra de estado" />
      <page pageid="205" ns="0" title="Barra de herramientas" />
      <page pageid="120" ns="0" title="Base de datos" />
      <page pageid="719" ns="0" title="Base de datos relacional" />
    </pages>
  </query>
</api>