then I modified the /usr/local/captiveportal/index.php file with:
LogoutWin.document.write('');
LogoutWin.document.write('') ;
LogoutWin.document.write('<title>Logout</title>') ;
LogoutWin.document.write(' ');
LogoutWin.document.write('') ;
LogoutWin.document.write(' ');
LogoutWin.document.write('') ;
LogoutWin.document.write('Click the button below to disconnect
');
LogoutWin.document.write('
<form id="dologout" name="dologout" method="POST" action="{$logouturl}">');
LogoutWin.document.write('');
LogoutWin.document.write('');
LogoutWin.document.write('</form>
');
LogoutWin.document.write('');
LogoutWin.document.write('');
LogoutWin.document.close();
/********************/
I am sure 100%