a.htm
---------------------------------------------------------
<html>
<head>
<script>
function GetFrmVal() {
var frm = document.frames["frm"];
alert(frm.document.all["divA"].innerHTML);
}
</script>
</head>
<body>
<input type="button" value="button" onclick="javascript:GetFrmVal();" type="button" />
<iframe id="frm" name="frm" src="http://www.blog.com.cn/b.htm" />
</body>
</html>
b.htm
------------------------------------------------------------------
<html>
<head>
</head>
<body>
<div id="divA" name="divA">DIVA</div>
</body>
</html>