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>
    <allfileusages gafcontinue="Biofuels.jpg|1478" />
  </query-continue>
  <query>
    <pages>
      <page pageid="147" ns="14" title="Category:Bailouts" />
      <page pageid="1127" ns="14" title="Category:Biodiversity" />
      <page pageid="1693" ns="0" title="Bill Hicks" />
      <page pageid="2634" ns="0" title="Beyond The Promised Land - The Movement and The Myth" />
      <page pageid="2755" ns="0" title="Ben Manski" />
      <page pageid="3103" ns="0" title="Bernie Sanders" />
      <page pageid="6154" ns="0" title="Category Gallery" />
      <page pageid="6905" ns="0" title="673 - The Language of The Vast Machine (The Ubiquitous Matrix Of Lies)" />
      <page pageid="6927" ns="14" title="Category:BIS" />
    </pages>
  </query>
</api>