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="543" ns="0" title="Dávková tvorba kazet s pomocí programu TURGEN" />
      <page pageid="129" ns="0" title="Fighter Pilot - Manuál" />
      <page pageid="152" ns="0" title="Stavíme RetroPCbestii" />
      <page pageid="513" ns="0" title="Tvorba kazet s pomocí programu TURGEN a obyčejného kazetového magnetofonu" />
      <page pageid="578" ns="0" title="Tvorba kazet s pomocí programu Turgen System a obyčejného kazetového magnetofonu" />
    </pages>
  </query>
</api>