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="2014-04-29T12:13:06Z" />
  </query-continue>
  <query>
    <blocks>
      <block id="648" user="JeanninUwi" by="JonGreen" timestamp="2014-04-29T12:16:52Z" expiry="infinity" reason="suspected spam user" nocreate="" autoblock="" />
      <block id="646" user="DelorasWhitson" by="JonGreen" timestamp="2014-04-29T12:16:32Z" expiry="infinity" reason="suspected spam user" nocreate="" autoblock="" />
      <block id="644" user="CallumSneddon" by="JonGreen" timestamp="2014-04-29T12:16:21Z" expiry="infinity" reason="suspected spam user" nocreate="" autoblock="" />
      <block id="642" user="LouanneWand" by="JonGreen" timestamp="2014-04-29T12:16:01Z" expiry="infinity" reason="Spamming links to external sites" nocreate="" autoblock="" />
      <block id="640" user="SantosBrandenbu" by="JonGreen" timestamp="2014-04-29T12:15:29Z" expiry="infinity" reason="suspected spam user" nocreate="" autoblock="" />
      <block id="638" user="SabineLODO" by="JonGreen" timestamp="2014-04-29T12:15:18Z" expiry="infinity" reason="Unacceptable username: Name fits common spammer pattern" nocreate="" autoblock="" />
      <block id="636" user="JanetteAMQA" by="JonGreen" timestamp="2014-04-29T12:15:05Z" expiry="infinity" reason="Spamming links to external sites" nocreate="" autoblock="" />
      <block id="634" user="BerylMetters" by="JonGreen" timestamp="2014-04-29T12:13:46Z" expiry="infinity" reason="Spamming links to external sites" nocreate="" autoblock="" />
      <block id="632" user="RudolphBreeze" by="JonGreen" timestamp="2014-04-29T12:13:34Z" expiry="infinity" reason="suspected spam user" nocreate="" autoblock="" />
      <block id="630" user="CorneliPLVG" by="JonGreen" timestamp="2014-04-29T12:13:22Z" expiry="infinity" reason="Unacceptable username: Name fits common spammer pattern" nocreate="" autoblock="" />
    </blocks>
  </query>
</api>