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="11103_Ivo_van_Haren.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="2691" ns="6" title="Bestand:&#039;t Slot.jpg" />
      <page pageid="1543" ns="6" title="Bestand:10087 Spoorwegovergang.jpg" />
      <page pageid="354" ns="6" title="Bestand:10216 Symphonieorkest.jpg" />
      <page pageid="1696" ns="6" title="Bestand:10430 Tentoonstelling 1903.jpg" />
      <page pageid="74" ns="6" title="Bestand:10471 moonen.jpg" />
      <page pageid="73" ns="6" title="Bestand:10481 heijst ld.jpg" />
      <page pageid="75" ns="6" title="Bestand:10483 grotenhuis.jpg" />
      <page pageid="86" ns="6" title="Bestand:10484 smeele.jpg" />
      <page pageid="1716" ns="6" title="Bestand:10490 Cafe Galgenwiel.jpg" />
      <page pageid="197" ns="6" title="Bestand:10823 Theodorus Arnoldus van Delft.jpg" />
    </pages>
  </query>
</api>