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>
  <warnings>
    <main xml:space="preserve">Unrecognized parameter: '*'</main>
  </warnings>
  <query-continue>
    <exturlusage euoffset="10" />
  </query-continue>
  <query>
    <exturlusage>
      <eu pageid="1864" ns="2" title="Usuario:ManuelRomero/DAW/TiposAplicaciones" url="http://www.mediawiki.org" />
      <eu pageid="3121" ns="2" title="Usuario:Lmorillas/Plataforma Innova/Documentacion" url="http://www.mediawiki.org/" />
      <eu pageid="1090" ns="0" title="LSWC scraping the web/taller scraping lwsc 2011" url="http://www.mediawiki.org/wiki/API:Client_code#API_Access_Libraries" />
      <eu pageid="3245" ns="2" title="Usuario:Lmorillas/Api WE" url="http://www.mediawiki.org/wiki/API:Main_page" />
      <eu pageid="3245" ns="2" title="Usuario:Lmorillas/Api WE" url="http://www.mediawiki.org/wiki/API:Tutorial" />
      <eu pageid="3293" ns="2" title="Usuario:Lmorillas/Plataforma Innova/Workflow" url="http://www.mediawiki.org/wiki/Article_Creation_Workflow" />
      <eu pageid="3293" ns="2" title="Usuario:Lmorillas/Plataforma Innova/Workflow" url="http://www.mediawiki.org/wiki/Article_Creation_Workflow/Design" />
      <eu pageid="3293" ns="2" title="Usuario:Lmorillas/Plataforma Innova/Workflow" url="http://www.mediawiki.org/wiki/Article_Creation_Workflow/Landing_System/Archive_1" />
      <eu pageid="3518" ns="2" title="Usuario:Lmorillas/Plataforma Innova/Frontend" url="http://www.mediawiki.org/wiki/Category:All_skins" />
      <eu pageid="3518" ns="2" title="Usuario:Lmorillas/Plataforma Innova/Frontend" url="http://www.mediawiki.org/wiki/Category:All_snippets" />
    </exturlusage>
  </query>
</api>