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="26" ns="6" title="File:Cave Run Lake.JPG" />
      <page pageid="23" ns="6" title="File:Dix Fog.jpg" />
      <page pageid="20" ns="6" title="File:Dix River Cliff.jpg" />
      <page pageid="17" ns="6" title="File:GreenRiver300Springs.jpg" />
      <page pageid="21" ns="6" title="File:Palisades.jpg" />
      <page pageid="12" ns="6" title="File:Patoka Lake Rock Quarry.jpeg" />
      <page pageid="574" ns="6" title="File:Pictured Rocks 086 7 8 tonemapped.jpg" />
    </pages>
  </query>
</api>