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>
    <blocks>
      <block id="126" user="TronyaSouther Resident" by="Oz Linden" timestamp="2013-12-09T18:22:57Z" expiry="infinity" reason="Inserting nonsense/gibberish into pages" nocreate="" autoblock="" />
      <block id="119" user="Kira Komarov" by="Fritz Linden" timestamp="2012-07-26T00:45:48Z" expiry="infinity" reason="Inserting nonsense/gibberish into pages" nocreate="" autoblock="" />
      <block id="72" user="Jer Straaf" by="Torley Linden" timestamp="2010-09-14T13:04:23Z" expiry="infinity" reason="Removing content from pages: Continuing to destructively degrade content, edit-war, and harass after my warning." nocreate="" autoblock="" noemail="" />
      <block id="18" user="Jumpman Gerje" by="Torley Linden" timestamp="2008-05-15T15:31:43Z" expiry="infinity" reason="Abusing multiple accounts: continued persistent vandalism and alt abuse" nocreate="" autoblock="" noemail="" allowusertalk="" />
      <block id="16" user="Jumpman Landau" by="Torley Linden" timestamp="2008-05-15T15:31:24Z" expiry="infinity" reason="Inserting nonsense/gibberish into pages: continued persistent vandalism and alt abuse" nocreate="" autoblock="" noemail="" allowusertalk="" />
      <block id="6" user="Jumpman Lane" by="Torley Linden" timestamp="2008-05-06T20:40:53Z" expiry="infinity" reason="Inserting nonsense/gibberish into pages" nocreate="" autoblock="" noemail="" allowusertalk="" />
      <block id="5" user="Lindobot Asbrink" by="Rob Linden" timestamp="2007-06-22T19:10:49Z" expiry="infinity" reason="Inserting nonsense/gibberish into pages: Very deliberate and persistent vandalism" nocreate="" autoblock="" allowusertalk="" />
    </blocks>
  </query>
</api>