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="006_1_quest.jpg" />
  </query-continue>
  <query>
    <pages>
      <page ns="6" title="File:001.png" missing="" />
      <page ns="6" title="File:002.png" missing="" />
      <page ns="6" title="File:003.png" missing="" />
      <page ns="6" title="File:004.png" missing="" />
      <page ns="6" title="File:005.png" missing="" />
      <page pageid="295" ns="6" title="File:001 luce ombra.jpg" />
      <page pageid="296" ns="6" title="File:002 uovo.jpg" />
      <page pageid="297" ns="6" title="File:003 palazzo.jpg" />
      <page pageid="298" ns="6" title="File:004 primo passo.jpg" />
      <page pageid="299" ns="6" title="File:005 1quest.jpg" />
    </pages>
  </query>
</api>