请问如下功能用firefox怎么实现？？？

<iframe id=demo width=500 height=500></iframe>  
<script>
demo.document.write('<img src="http://www.google.cn/intl/zh-CN/images/logo_cn.gif">');
demo.document.write('<br/>点击图片调整大小');
demo.document.designMode="on"
</script>

没人看吗自己顶

Setting document.designMode must NOT be done in the script section of the head. We suggest the onLoad function for the body where the iframe is contained.