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="4268" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <revisions>
          <rev user="Ben" timestamp="2012-07-18T19:14:06Z" comment="Spruced up the front page with graphics" />
          <rev user="Ben" timestamp="2012-07-16T16:54:47Z" comment="" />
          <rev user="WikiSysop" timestamp="2012-06-20T18:19:04Z" comment="" />
          <rev user="Ben" timestamp="2011-09-28T15:31:28Z" comment="" />
          <rev user="Ben" timestamp="2011-09-28T15:24:53Z" comment="Added news feed back to main page. XFeed extension broke, so now using Feedimport." />
        </revisions>
      </page>
    </pages>
  </query>
</api>