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="20070818232639_109.png" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1816" ns="6" title="File:12345.JPG" />
      <page pageid="1500" ns="6" title="File:20070804002556 748.png" />
      <page pageid="1501" ns="6" title="File:20070806002543 362.png" />
      <page pageid="1502" ns="6" title="File:20070806003207 040.png" />
      <page pageid="1503" ns="6" title="File:20070806003217 802.png" />
      <page pageid="1504" ns="6" title="File:20070806003223 734.png" />
      <page pageid="1515" ns="6" title="File:20070818230241 308.png" />
      <page pageid="1516" ns="6" title="File:20070818232526 136.png" />
      <page pageid="1517" ns="6" title="File:20070818232619 643.png" />
      <page pageid="1518" ns="6" title="File:20070818232628 334.png" />
    </pages>
  </query>
</api>