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HTML is good for debugging, but probably is not suitable for your application.
See complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <allcategories>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Alabama - Community Members</c>
      <c size="234" pages="234" files="0" subcats="0" xml:space="preserve">Alabama - Game Sites</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">Alaska - Community Members</c>
      <c size="127" pages="127" files="0" subcats="0" xml:space="preserve">Alaska - Game Sites</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">Alberta - Community Members</c>
      <c size="232" pages="232" files="0" subcats="0" xml:space="preserve">Alberta - Game Sites</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">Algeria - Game Sites</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">American Samoa - Community Members</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">Antigua and Barbuda - Community Members</c>
      <c size="75" pages="75" files="0" subcats="0" xml:space="preserve">Applications</c>
    </allcategories>
  </query>
  <query-continue>
    <allcategories acfrom="Argentina - Community Members" />
  </query-continue>
</api>