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>
    <allpages apcontinue="CSS_box_model" />
  </query-continue>
  <query>
    <allpages>
      <p pageid="475" ns="0" title="Backups en GNU/Linux" />
      <p pageid="318" ns="0" title="Bases de dades" />
      <p pageid="469" ns="0" title="Bash script" />
      <p pageid="494" ns="0" title="Batalla naval en PHP" />
      <p pageid="421" ns="0" title="Bones pràctiques de programació" />
      <p pageid="313" ns="0" title="Buildout" />
      <p pageid="526" ns="0" title="CMS" />
      <p pageid="257" ns="0" title="CMS backup and restoring" />
      <p pageid="215" ns="0" title="CSS adreçament" />
      <p pageid="212" ns="0" title="CSS basics" />
    </allpages>
  </query>
</api>