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>
    <random>
      <page id="113" ns="0" title="The Art and Science of Systems Biology" />
      <page id="46" ns="0" title="Understanding adaptive immunity: a crossroad of the physical and life sciences" />
    </random>
  </query>
</api>