You are looking at the HTML representation of the XML format.
HTML is good for debugging, but probably is not suitable for your application.
See complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <pages>
      <page ns="0" title="Main Page" missing="" />
    </pages>
    <general mainpage="Hauptseite" base="http://wiki.linuxgaming.de/index.php/Hauptseite" sitename="Spielen-unter-Linux Wiki by linuxgaming.de" generator="MediaWiki 1.14.1" case="first-letter" rights="Creative Common - Namensnennung-Weitergabe unter gleichen Bedingungen 3.0 Deutschland (CC BY-SA 3.0) " lang="de" fallback8bitEncoding="windows-1252" writeapi="" timezone="UTC" timeoffset="0" />
  </query>
</api>