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>
    <pages>
      <page pageid="253" ns="0" title="Davis Vantage Vue" />
      <page pageid="547" ns="0" title="FAQ WX" />
      <page pageid="483" ns="0" title="FAQ WeeWX" />
      <page pageid="619" ns="0" title="Software webcam" />
      <page pageid="113" ns="0" title="Visual Start Meteoclimatic" />
      <page pageid="503" ns="0" title="WDconsole RPI" />
      <page pageid="348" ns="0" title="¿Donde puedo localizar los driver del datalogger para Windows?" />
    </pages>
  </query>
</api>