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="120" ns="0" title="Boerner, Otto Alexander" />
      <page pageid="712" ns="0" title="Fankhauser, Franz" />
      <page pageid="347" ns="0" title="Horning, Adolf Benjamin" />
      <page pageid="386" ns="0" title="Kausler, Heinrich Eduard von" />
      <page pageid="541" ns="0" title="Noyer-Weidner, Alfred Alexander Friedrich" />
      <page pageid="744" ns="0" title="Schjerve Rindler, Rosita" />
      <page pageid="831" ns="0" title="Ten Brink, Bernhard Aegidius Konrad (auch: Barend bzw. Bernard)" />
      <page pageid="889" ns="0" title="Wiese, Berthold Heinrich Friedrich" />
      <page pageid="901" ns="0" title="Wurzbach Ritter von Tannenberg, Alfred Wolfgang von" />
    </pages>
  </query>
</api>