function Launch(page) {
topp = (screen.height - 500) / 2;
lleft = (screen.width - 500 )/ 2;
pop = window.open(page, "impressum", "toolbar=no,location=no,scrollbars=no,status=no,resizable=no,width=500,height=500,left="+lleft+",top="+topp+"");
}