execCommand的问题

兼容版~IE,FF,opera,safari:<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" 
"http://www.w3.org/TR/html4/strict.dtd">
<html>
  <head>
    <title>Rank's HTML document</title>
    <meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
    <meta http-equiv="Pragma" content="no-cache" />  
    <meta http-equiv="Cache-Control" content="no-cache" />     
    <meta http-equiv="Expires" content="0" />
    <meta http-equiv="ImageToolbar" content="no" />
    <meta http-equiv="Creator.name" content="Rank, BlueDestiny, never-online" />
    <style type="text/css" title="default" media="screen">
    /*<![CDATA[*/    /*]]>*/
    </style>    </head>
  <body>
<script type="text/javascript">//<![CDATA[
onload = function () {
function insertBox(id) { return '<input id="' +id+ '" value="never-online.net/blog">'; }
var sHTML = insertBox('myid') +'<a href="http://www.never-online.net">never-online</a>';
var iframe=document.getElementById('frm').contentWindow;
iframe.document.designMode="on";
iframe.document.writeln('<body id="never-online.net"></body>');
if(!!window.ActiveXObject) {
iframe.document.body.focus();
var doc=iframe.document;
var range= doc.selection.createRange();
if(doc.selection.type=="Control") {
var range2=doc.body.createTextRange();
range2.moveToElementText(range.item(0));
range2.select();
range=range2;
}
range.pasteHTML(sHTML);
} else {
iframe.document.execCommand('insertHTML',false,sHTML); 
}
alert(iframe.document.body.innerHTML)
}//]]></script>
<iframe src="about:blank" id="frm"></iframe>
  </body>
</html>