function bildanzeige(dateiname) {
    document.close();
    document.open();
    document.write('<link rel=stylesheet type="text/css" media="screen" href="/stil.css">');
    document.write('<br /><table width="100%" height="100%"><tr><td align="center" valign="center"><img src="'+dateiname+'" border="1" />');
    document.write('<br /><br /><a href="javascript:history.back()">zur&uuml;ck</a></table>');
    document.close();
  }