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="Ceed_layout.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1921" ns="6" title="File:6692006541 d06c1c6757 o.jpg" />
      <page pageid="1953" ns="6" title="File:Boostconfig.png" />
      <page pageid="1859" ns="6" title="File:CEGUI-SDL-all-widgets.png" />
      <page pageid="1860" ns="6" title="File:CEGUI-SDL-hello-world.png" />
      <page pageid="1888" ns="6" title="File:Ceed application settings.png" />
      <page pageid="1880" ns="6" title="File:Ceed contrib import repo.png" />
      <page pageid="1881" ns="6" title="File:Ceed contrib import repo done.png" />
      <page pageid="1883" ns="6" title="File:Ceed contrib push.png" />
      <page pageid="1886" ns="6" title="File:Ceed imageset.png" />
      <page pageid="1887" ns="6" title="File:Ceed imageset create image.png" />
    </pages>
  </query>
</api>