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>
    <blocks bkstart="2011-02-10T00:37:14Z" />
  </query-continue>
  <query>
    <blocks>
      <block id="11" user="46.118.158.25" by="Al" timestamp="2014-01-24T20:44:23Z" expiry="infinity" reason="Añadir información falsa" anononly="" nocreate="" />
      <block id="10" user="Seymour46ahlcgmts" by="Al" timestamp="2013-12-04T02:15:38Z" expiry="infinity" reason="Spammer" nocreate="" autoblock="" noemail="" />
      <block id="9" user="91.200.14.96" by="Al" timestamp="2013-11-24T22:38:35Z" expiry="infinity" reason="Añadir basura a las páginas" nocreate="" noemail="" />
      <block id="8" user="190.66.17.53" by="Pablog" timestamp="2012-04-18T19:23:43Z" expiry="infinity" reason="spam" anononly="" nocreate="" />
      <block id="7" user="119.46.110.203" by="Pablog" timestamp="2012-04-18T19:22:13Z" expiry="infinity" reason="spam" anononly="" nocreate="" />
      <block id="6" user="190.151.144.25" by="Pablog" timestamp="2012-04-02T00:31:23Z" expiry="infinity" reason="spam" nocreate="" noemail="" />
      <block id="5" user="46.29.253.210" by="Pablog" timestamp="2012-03-14T20:01:19Z" expiry="infinity" reason="spam" anononly="" nocreate="" />
      <block id="4" user="46.33.241.195" by="Pablog" timestamp="2012-02-07T01:31:14Z" expiry="infinity" reason="spam" anononly="" nocreate="" />
      <block id="3" user="176.65.164.111" by="Pablog" timestamp="2012-02-05T01:44:42Z" expiry="infinity" reason="spam" anononly="" nocreate="" />
      <block id="2" user="199.15.234.40" by="WikiSysop" timestamp="2011-11-23T01:03:46Z" expiry="infinity" reason="Publicitar enlaces a otras páginas web" anononly="" nocreate="" />
    </blocks>
  </query>
</api>