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>
    <allcategories accontinue="Južna_Evropa" />
  </query-continue>
  <query>
    <allcategories>
      <c size="22" pages="22" files="0" subcats="0" xml:space="preserve">Afrika</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">All destination articles</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">Articles needing IsPartOf category</c>
      <c size="10" pages="10" files="0" subcats="0" xml:space="preserve">Avstralija in Oceanija</c>
      <c size="42" pages="42" files="0" subcats="0" xml:space="preserve">Azija</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">Egipt</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">Evropa</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">Jugovzgodna Evropa</c>
      <c size="11" pages="11" files="0" subcats="0" xml:space="preserve">Jugovzhodna Evropa</c>
      <c size="12" pages="12" files="0" subcats="0" xml:space="preserve">Južna Amerika</c>
    </allcategories>
  </query>
</api>