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>
    <alltransclusions gatcontinue="Note|566" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page" />
      <page pageid="304" ns="0" title="PXV:IIXC Inst Page CreateFromMemory" />
      <page pageid="307" ns="0" title="PXV:IIXC Page AdjustHLS" />
      <page pageid="311" ns="0" title="PXV:IIXC Page AutoContrast" />
      <page pageid="313" ns="0" title="PXV:IIXC Page ColorBalance" />
      <page pageid="317" ns="0" title="PXV:IIXC Page Correction" />
      <page pageid="326" ns="0" title="PXV:IIXC Page FilterNoise" />
      <page pageid="333" ns="0" title="PXV:IIXC Page Invert" />
      <page pageid="334" ns="0" title="PXV:IIXC Page InvertChannel" />
    </pages>
  </query>
</api>