function impressum()
{
	 x_koord = Math.round(Math.max((screen.width - 400) / 2,0));
	 y_koord = Math.round(Math.max((screen.height - 400) / 2,0));
	 var f = window.open('http://www.altehandwerksmeister.de/impressum.htm','impressum','left='+x_koord+',top='+y_koord+',height=400,width=400,status=no,locationbar=no,menubar=no,resizable=yes,scrollbars=yes');
	 return false;
}