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="Van_Hool_A507" />
  </query-continue>
  <query>
    <allpages>
      <p pageid="265" ns="0" title="Irisbus Agora S" />
      <p pageid="266" ns="0" title="Irisbus Agora S CNG" />
      <p pageid="269" ns="0" title="Irisbus Citelis 12 CNG" />
      <p pageid="70" ns="0" title="Main Page" />
      <p pageid="243" ns="0" title="Mercedes Benz O405N" />
      <p pageid="264" ns="0" title="Renault Agora S CNG" />
      <p pageid="267" ns="0" title="Solaris Urbino III 18" />
      <p pageid="268" ns="0" title="Solaris Urbino III 8,6" />
      <p pageid="821" ns="0" title="Stadler GTW 2/6 &quot;RailBus&quot;" />
      <p pageid="252" ns="0" title="Test" />
    </allpages>
  </query>
</api>