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="Como_aprovechar_nuestros_datos_wunderground" />
  </query-continue>
  <query>
    <pages>
      <page pageid="450" ns="0" title="Bird Spikes" />
      <page pageid="205" ns="0" title="Borrardatos" />
      <page pageid="696" ns="0" title="CONSOLAS-FINEOFFSET" />
      <page pageid="417" ns="0" title="Cacharreo" />
      <page pageid="602" ns="0" title="Calefactar Davis Vantage Vue" />
      <page pageid="614" ns="0" title="Calibracion pluviometro Davis Vantage Pro2" />
      <page pageid="649" ns="0" title="Cambiar higrómetro por otro compatible" />
      <page pageid="195" ns="0" title="Cambio de estación" />
      <page pageid="196" ns="0" title="Cambio de ubicacion" />
      <page pageid="471" ns="0" title="Como alimentar Davis USB" />
    </pages>
  </query>
</api>