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="Básicas_para_la_instalación" />
  </query-continue>
  <query>
    <pages>
      <page ns="0" title="Bugs Conocidos GXtest Designer" missing="" />
      <page ns="0" title="Bugs Conocidos GXtest Manager" missing="" />
      <page pageid="253" ns="0" title="Basic Configurations in GXtest Manager" />
      <page pageid="321" ns="0" title="Basics to the installation" />
      <page pageid="539" ns="0" title="Best Practices automating with GXtest" />
      <page pageid="538" ns="0" title="Buenas Prácticas de Automatización con GXtest" />
      <page pageid="282" ns="0" title="Bugs Conocidos GXtest" />
      <page pageid="838" ns="0" title="Building JMeter scripts with GXtest" />
      <page pageid="836" ns="0" title="Building OpenSTA scripts with GXtest" />
      <page pageid="267" ns="0" title="Builds de GXtest 1.1 Beta" />
    </pages>
  </query>
</api>