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="20150420103219" timestamp="2015-04-20T10:32:19Z" ns="0" title="Servicios On-Line" />
        <page value="20150420103235" timestamp="2015-04-20T10:32:35Z" ns="0" title="Herramientas de programación para las comunidades virtuales" />
        <page value="20150420103250" timestamp="2015-04-20T10:32:50Z" ns="0" title="Software libre" />
        <page value="20150420103304" timestamp="2015-04-20T10:33:04Z" ns="0" title="Redes P2P móviles" />
        <page value="20150421122207" timestamp="2015-04-21T12:22:07Z" ns="0" title="FUNCIONAMIENTO" />
        <page value="20150421123107" timestamp="2015-04-21T12:31:07Z" ns="0" title="Redes Sociales" />
        <page value="20150423120016" timestamp="2015-04-23T12:00:16Z" ns="0" title="Youtube" />
        <page value="20150423120629" timestamp="2015-04-23T12:06:29Z" ns="0" title="UMTS" />
        <page value="20150423121418" timestamp="2015-04-23T12:14:18Z" ns="0" title="Windows Media Player" />
        <page value="20150423121642" timestamp="2015-04-23T12:16:42Z" ns="0" title="3G" />
      </results>
    </querypage>
  </query>
</api>