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>
    <querypage qpoffset="10" />
  </query-continue>
  <query>
    <querypage name="Ancientpages">
      <results>
        <page value="20140919182450" timestamp="2014-09-19T18:24:50Z" ns="0" title="Página principal" />
        <page value="20140922142623" timestamp="2014-09-22T14:26:23Z" ns="0" title="Planificación de la actividad preventiva" />
        <page value="20140924063121" timestamp="2014-09-24T06:31:21Z" ns="0" title="Plan de prevención" />
        <page value="20140926073058" timestamp="2014-09-26T07:30:58Z" ns="0" title="Trabajador designado" />
        <page value="20140926084158" timestamp="2014-09-26T08:41:58Z" ns="0" title="Servicio de Prevención Propio" />
        <page value="20140926110306" timestamp="2014-09-26T11:03:06Z" ns="0" title="Servicio de Prevención Ajeno" />
        <page value="20140929114025" timestamp="2014-09-29T11:40:25Z" ns="0" title="Servicio de Prevención Mancomunado" />
        <page value="20140930062106" timestamp="2014-09-30T06:21:06Z" ns="0" title="Comité de Seguridad y Salud" />
        <page value="20140930065126" timestamp="2014-09-30T06:51:26Z" ns="0" title="Condiciones de trabajo" />
        <page value="20140930065326" timestamp="2014-09-30T06:53:26Z" ns="0" title="Potencialmente peligroso" />
      </results>
    </querypage>
  </query>
</api>