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>
    <allpages gapcontinue="Search_Engine_Optimization" />
  </query-continue>
  <query>
    <pages>
      <page pageid="262" ns="0" title="Release History">
        <revisions>
          <rev contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">AbleCommerce GOLD [http://help.ablecommerce.com/index.htm#upgrades/acgold/change_logs.htm Release History]</rev>
        </revisions>
      </page>
      <page pageid="19" ns="0" title="Running Your Store">
        <revisions>
          <rev contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">* [[Fraud Prevention]]
* [[Marketing Campaigns]]
* [[Getting into search engines with Sitemap]]
* [[Making the most of the custom Order Status feature]]</rev>
        </revisions>
      </page>
    </pages>
  </query>
</api>