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>
    <querypage qpoffset="10" />
  </query-continue>
  <query>
    <querypage name="Ancientpages">
      <results>
        <page value="20160603122646" timestamp="2016-06-03T12:26:46Z" ns="0" title="Etat des travaux" />
        <page value="20160603123348" timestamp="2016-06-03T12:33:48Z" ns="0" title="Administrativia" />
        <page value="20160613130415" timestamp="2016-06-13T13:04:15Z" ns="0" title="YK: History of MediaWiki" />
        <page value="20160613130614" timestamp="2016-06-13T13:06:14Z" ns="0" title="YK: Community and support" />
        <page value="20160613131122" timestamp="2016-06-13T13:11:22Z" ns="0" title="YK: Available hosts" />
        <page value="20160613215923" timestamp="2016-06-13T21:59:23Z" ns="0" title="YK: Chapter 23: MediaWiki development: a guide for the accidental developer" />
        <page value="20160613223149" timestamp="2016-06-13T22:31:49Z" ns="0" title="YK: Chapter 22: Running a successful wiki" />
        <page value="20160613223327" timestamp="2016-06-13T22:33:27Z" ns="0" title="YK: Chapter 21: Importing and exporting" />
        <page value="20160613223503" timestamp="2016-06-13T22:35:03Z" ns="0" title="YK: Chapter 20: External data and applications" />
        <page value="20160613223819" timestamp="2016-06-13T22:38:19Z" ns="0" title="YK: Chapter 19: Additional Semantic MediaWiki functionality" />
      </results>
    </querypage>
  </query>
</api>