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>
    <pages>
      <page pageid="42" ns="0" title="Windows xp Tipps, Tricks &amp; Einstellungen" />
      <page pageid="74" ns="0" title="Citrix® Receiver x86-Client Version 11 auf Microsoft Windows 7 Professional SP1 installieren (Version 6.1.7601)" />
      <page pageid="86" ns="0" title="Webserver mit FreeBSD® 7.2 über Ports aufsetzen" />
      <page pageid="141" ns="0" title="Windows xp, 7 Tipps, Tricks &amp; Einstellungen" />
    </pages>
  </query>
</api>