You are looking at the HTML representation of the mFormat?> format.
HTML is good for debugging, but probably is not suitable for your application.
Please see "format" parameter documentation at the API help for more information. 
<?xml version="1.0" encoding="utf-8"?>
<api>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <revisions>
          <rev revid="1" pageid="1" oldid="1" user="MediaWiki default" anon="" timestamp="2007-08-23T15:51:13Z" />
          <rev revid="2" pageid="1" oldid="2" user="FredericBaud" timestamp="2007-08-24T08:41:00Z" comment="initial creation" />
          <rev revid="3" pageid="1" oldid="3" user="FredericBaud" minor="" timestamp="2007-08-24T08:57:33Z" />
          <rev revid="4" pageid="1" oldid="4" user="FredericBaud" minor="" timestamp="2007-08-24T10:04:50Z" comment="/* Other languages */" />
          <rev revid="5" pageid="1" oldid="5" user="FredericBaud" minor="" timestamp="2007-08-24T11:58:38Z" />
        </revisions>
      </page>
    </pages>
  </query>
  <query-continue>
    <revisions rvstartid="7" />
  </query-continue>
</api>