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>
    <pageswithprop>
      <page pageid="191" ns="4" title="Name wiki:Über Schachklub.info" value="&lt;span style=&quot;position: absolute; clip: rect(1px 1px 1px 1px); clip: rect(1px, 1px, 1px, 1px);&quot;&gt;Name wiki:Über Schachklub.info&lt;/span&gt;" />
      <page pageid="213" ns="0" title="Archiv" value="&lt;span style=&quot;position: absolute; clip: rect(1px 1px 1px 1px); clip: rect(1px, 1px, 1px, 1px);&quot;&gt;Archiv&lt;/span&gt;" />
    </pageswithprop>
  </query>
</api>