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>
    <allfileusages gafcontinue="Immagine_eclipse2.png|39" />
  </query-continue>
  <query>
    <pages>
      <page pageid="10" ns="0" title="Diagrammi di flusso e Codice Matlab" />
      <page pageid="39" ns="0" title="Configurazione dell&#039;ambiente di sviluppo Java" />
      <page pageid="48" ns="0" title="Strutture dati" />
      <page pageid="52" ns="0" title="Risoluzione Tracce di Esame II Modulo" />
    </pages>
  </query>
</api>