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>
    <allcategories>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">AP Alliance Dominion Zetran</c>
      <c size="8" pages="8" files="0" subcats="0" xml:space="preserve">AP Alliance Melrehns</c>
      <c size="6" pages="6" files="0" subcats="0" xml:space="preserve">AP Alliance de l'Empire Amaranth</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">AP Alliance de la Fédération Thelios</c>
      <c size="7" pages="7" files="0" subcats="0" xml:space="preserve">AP Alliance de la Fédération Thélios</c>
      <c size="6" pages="6" files="0" subcats="0" xml:space="preserve">AP Alliance de la RCA</c>
      <c size="2" pages="2" files="0" subcats="0" xml:space="preserve">AP Alliance des Domaines Ducaux</c>
      <c size="8" pages="8" files="0" subcats="0" xml:space="preserve">AP Alliance du Cercle Léanth</c>
      <c size="10" pages="10" files="0" subcats="0" xml:space="preserve">AP Alliance du Dominion Zetran</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">AP Gouverneur de la Fédération Thélios</c>
    </allcategories>
  </query>
  <query-continue>
    <allcategories accontinue="AP_Gouverneur_du_Dominion_Zetran" />
  </query-continue>
</api>