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="26" />
  </query-continue>
  <query>
    <pages>
      <page pageid="279" ns="0" title="Main Page">
        <revisions>
          <rev user="MediaWiki default" anon="" timestamp="2009-02-03T09:39:33Z" comment="" />
          <rev user="Admin" timestamp="2009-02-03T10:58:51Z" comment="Home" />
          <rev user="Admin" timestamp="2009-02-03T11:01:47Z" comment="New page: &#039;&#039;&#039;Project title&#039;&#039;&#039;  FORECASTER: &#039;&#039;&#039;F&#039;&#039;&#039;acilitating the application of &#039;&#039;&#039;O&#039;&#039;&#039;utput from &#039;&#039;&#039;R&#039;&#039;&#039;esearch and &#039;&#039;&#039;CA&#039;&#039;&#039;se &#039;&#039;&#039;ST&#039;&#039;&#039;udies on &#039;&#039;&#039;E&#039;&#039;&#039;cological &#039;&#039;&#039;R&#039;&#039;&#039;esponses to hydro-morphologi..." />
          <rev user="Admin" timestamp="2009-02-03T11:04:54Z" comment="" />
          <rev user="Admin" timestamp="2009-02-05T09:50:36Z" comment="" />
        </revisions>
      </page>
    </pages>
  </query>
</api>