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HTML is good for debugging, but probably is not suitable for your application.
See complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <images>
          <im ns="6" title="File:Addon-install.png" />
          <im ns="6" title="File:Addon-popup.png" />
          <im ns="6" title="File:Masjid-art.jpg" />
        </images>
      </page>
    </pages>
  </query>
</api>