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-continue>
    <allimages gaicontinue="Aglor_display.gif" />
  </query-continue>
  <query>
    <pages>
      <page pageid="257" ns="6" title="File:AFFOREST(ation) strategies.png" />
      <page pageid="258" ns="6" title="File:AFFOREST Graphical window.png" />
      <page pageid="260" ns="6" title="File:AFFOREST output settings.png" />
      <page pageid="259" ns="6" title="File:AFFOREST questions.png" />
      <page pageid="255" ns="6" title="File:Afforest.gif" />
      <page pageid="371" ns="6" title="File:Agflor input.gif" />
      <page pageid="373" ns="6" title="File:Agflor modules.gif" />
      <page pageid="372" ns="6" title="File:Agflor res.gif" />
      <page pageid="369" ns="6" title="File:Agflor study area.gif">
        <duplicatefiles>
          <df name="Aglor_study_area.gif" user="Joseborges" timestamp="2009-10-08T12:05:59Z" />
        </duplicatefiles>
      </page>
      <page pageid="367" ns="6" title="File:Agflorpresentation.gif" />
    </pages>
  </query>
</api>