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="Linode_a_records.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="749" ns="6" title="File:Blueshift screenshot.png" />
      <page pageid="748" ns="6" title="File:Celerity screenshot.png" />
      <page pageid="732" ns="6" title="File:Dreamwidth1-80x15.gif" />
      <page pageid="729" ns="6" title="File:Dreamwidth1.gif" />
      <page pageid="730" ns="6" title="File:Dreamwidth2.gif" />
      <page pageid="731" ns="6" title="File:Dreamwidth3.gif" />
      <page pageid="182" ns="6" title="File:Dreamwidth Studios- Operating Agreement.doc" />
      <page pageid="824" ns="6" title="File:Gedit-tabs.png" />
      <page pageid="751" ns="6" title="File:Gradation horizontal screenshot.png" />
      <page pageid="752" ns="6" title="File:Gradation sidebar screenshot.png" />
    </pages>
  </query>
</api>