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="5" ns="0" title="Using OpenID" />
      <page pageid="43" ns="0" title="Roger Gracie BJJ Competion Breakdown" />
      <page pageid="12" ns="0" title="Image Synthesis" />
      <page pageid="10" ns="0" title="Interviewing a Technical Candidate" />
      <page pageid="3" ns="0" title="Writing Tips" />
      <page pageid="41" ns="0" title="Building Your Resume" />
      <page pageid="40" ns="0" title="Juniper Pulse on 64-bit Linux" />
      <page pageid="11" ns="0" title="Computer Graphics" />
    </pages>
  </query>
</api>