在IE中iframe或者frame的contentWindow属性可以省略，但在Firefox中如果要对iframe对象进行编辑则
必须指定contentWindow属性。
function EnableEdit()
{
var editor;
editor = document.getElementById("HtmlEdit").contentWindow;
// 针对IE浏览器, make it editable
editor.document.designMode = 'On';
editor.document.contentEditable = true;
// For compatible with FireFox, it should open and write something to make it work
editor.document.open();
editor.document.writeln('<html><head>');
editor.document.writeln('<style>body {background: white;font-size:9pt;margin: 2px; padding: 0px;}</style>');
editor.document.writeln('</head><body></body></html>');
editor.document.close();
}
<iframe ID="HtmlEdit" MARGINHEIGHT="1" MARGINWIDTH="1" width="100%" height="312">
</iframe>
<html>
<body>
<script>
var ifr = document.createElement("iframe");
document.body.appendChild(ifr);
var ifrdoc = ifr.contentWindow.document;
var s = fixingHTB.innerHTML; //进入可编辑模式前存好
ifrdoc.designMode = "on"; //文档进入可编辑模式
ifrdoc.open(); //打开流
ifrdoc.write(s);
ifrdoc.close(); //关闭流
ifrdoc.designMode ="off"; //文档进入非可编辑模式
</script>
</body>
</html>
