iframe内嵌页面无法刷新(非frame)

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=Shift_JIS">
</head><body>
<iframe name="ifr1" src="iframeHidden.htm"></iframe>
<form name="form1" method="post" action="">
  <input type="button" name="Button" value="Button" onclick="document.ifr1.location.href='postinfo.html'">
  <input type="button" name="Button" value="Show Iframe InnerHTML" onclick='alert(ifr1.window.document.body.innerHTML)'>
  <input type="button" name="Button" value="SET Iframe scrollTop" onclick='ifr1.document.body.scrollTop =0'>
  <input type="button" name="Button" value="reload" onclick='ifr1.location.reload()'>
</form>
</body>
</html>