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>
    <allimages gaicontinue="Tabel621.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="87" ns="6" title="File:3GPP TM RD-8cd3d.jpg" />
      <page pageid="86" ns="6" title="File:ETSI header logo.gif" />
      <page pageid="88" ns="6" title="File:Gsm.jpeg" />
      <page pageid="89" ns="6" title="File:Modelling principles.png" />
      <page pageid="103" ns="6" title="File:Network initiated failover.png" />
      <page pageid="101" ns="6" title="File:Network initiated ussd.png" />
      <page pageid="95" ns="6" title="File:PLMN config.png" />
      <page pageid="90" ns="6" title="File:Tabel611.png" />
      <page pageid="91" ns="6" title="File:Tabel6111.png" />
      <page pageid="92" ns="6" title="File:Tabel612.png" />
    </pages>
  </query>
</api>