function switchlang(tolan) {
  thishref = top.location.href;
  if (thishref.indexOf('lang=eng')<0 && thishref.indexOf('lang=chi')<0 && thishref.indexOf('eng')<0 && thishref.indexOf('chi')<0) {
    if (thishref.indexOf('?')<0 && thishref.indexOf('%3F')<0) {
        thishref=thishref+'?lang='+tolan;
    } else {
        thishref=thishref+'&lang='+tolan;
    }
  }
  if (tolan == 'eng') {
    top.location.href=thishref.replace(/chi/gi,"eng");
  } else {
    top.location.href=thishref.replace(/eng/gi,"chi");
  }
}