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>
    <alltransclusions gatcontinue="Trip_report|84" />
  </query-continue>
  <query>
    <pages>
      <page pageid="48" ns="0" title="1st Digital Agenda Assembly" />
      <page pageid="57" ns="0" title="Reasoning Web 2010 Summer School" />
      <page pageid="58" ns="0" title="IWK - 55th International Scientific Colloquium (IWK)" />
      <page pageid="59" ns="0" title="ESWC 2011 Summer School" />
      <page pageid="60" ns="0" title="ESWC 2011" />
      <page pageid="61" ns="0" title="ESWC 2012" />
      <page pageid="70" ns="0" title="Working Meeting on DDI-RDF Discovery Meeting" />
      <page pageid="72" ns="0" title="Wikimania 2010" />
      <page pageid="75" ns="0" title="SMWCon Fall 2013" />
      <page pageid="76" ns="0" title="ESWC 2013" />
    </pages>
  </query>
</api>