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="77" pageid="1" oldid="85" user="Bankhippy" comment="/* Compass */ added online banking and main street banking" />
        </revisions>
      </page>
    </pages>
    <general mainpage="Main Page" base="http://www.barcampbank.org/index.php/Main_Page" sitename="BarCampBank's Wiki" generator="MediaWiki 1.10.1" case="first-letter" rights="" />
  </query>
</api>