function getPara() {
  var str,parastr;
  str = window.location.search;
  parastr = str.substring(1);
  return parastr;
}
function getSub(para) {
  return para.substring(para.indexOf('sub=') + 4);
}
function goSub() {
  sub = getSub(getPara());
  if (sub != '') {
    document.getElementById('topic').innerHTML = '<iframe marginwidth=0 marginheight=0 src=' + sub + ' id=topicFrame name=topicFrame frameborder=0 width=100% scrolling=no onload=\'this.height=topicFrame.document.body.scrollHeight\'></iframe>';
  } else {
    alert('error');
  }
}