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>
    <revisions rvcontinue="47" />
  </query-continue>
  <query>
    <pages>
      <page pageid="2" ns="0" title="Main Page">
        <revisions>
          <rev user="BerkmanSysop" timestamp="2007-09-24T20:51:13Z" comment="New page: &lt;big&gt;&#039;&#039;&#039;Welcome to your new Berkman Center wiki!&#039;&#039;&#039;&lt;/big&gt;  Consult the [http://meta.wikimedia.org/wiki/Help:Contents User&#039;s Guide] for information on using the wiki software.  When you are..." />
          <rev user="WikiSysop" timestamp="2010-05-13T17:44:55Z" comment="" />
          <rev user="WikiSysop" timestamp="2010-05-13T18:08:05Z" comment="" />
          <rev user="WikiSysop" timestamp="2010-05-18T19:34:11Z" comment="" />
          <rev user="WikiSysop" timestamp="2010-05-18T19:35:20Z" comment="" />
        </revisions>
      </page>
    </pages>
  </query>
</api>