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>
    <pages>
      <page pageid="5" ns="0" title="Account tree" contentmodel="wikitext" pagelanguage="en" touched="2014-07-18T13:11:11Z" lastrevid="38" counter="52973" length="6374" />
      <page pageid="8" ns="0" title="Cryptonite" contentmodel="wikitext" pagelanguage="en" touched="2014-09-03T11:42:02Z" lastrevid="65" counter="67001" length="2135" />
      <page pageid="11" ns="0" title="Dynamic max block size" contentmodel="wikitext" pagelanguage="en" touched="2014-07-16T06:36:43Z" lastrevid="11" counter="21835" length="1562" new="" />
      <page pageid="17" ns="0" title="Mini-blockchain" contentmodel="wikitext" pagelanguage="en" touched="2014-11-04T22:56:12Z" lastrevid="67" counter="27874" length="3308" />
      <page pageid="20" ns="0" title="Mini-blockchain scheme" contentmodel="wikitext" pagelanguage="en" touched="2014-07-16T08:46:16Z" lastrevid="22" counter="76236" length="2061" new="" />
      <page pageid="22" ns="0" title="Network synchronization" contentmodel="wikitext" pagelanguage="en" touched="2014-07-18T12:25:43Z" lastrevid="26" counter="10192" length="3037" new="" />
      <page pageid="29" ns="0" title="Weaknesses and attack vectors" contentmodel="wikitext" pagelanguage="en" touched="2014-08-01T03:45:59Z" lastrevid="62" counter="64764" length="5201" />
      <page pageid="30" ns="0" title="Withdrawal limits" contentmodel="wikitext" pagelanguage="en" touched="2014-07-26T19:05:03Z" lastrevid="59" counter="85307" length="5523" />
    </pages>
  </query>
</api>