iframe自适应

方法1，（缺点，高度自动扩展后，height不会恢复）

<iframe id="frame_content" src="iframe_b.html" scrolling="no" frameborder="0" onload="this.height=100"></iframe>

<script type="text/javascript">

function reinitIframe(){

var iframe = document.getElementById("frame_content");

try{

var bHeight = iframe.contentWindow.document.body.scrollHeight;

var dHeight = iframe.contentWindow.document.documentElement.scrollHeight;

var height = Math.max(bHeight, dHeight);

iframe.height =  height;

}catch (ex){}

}

window.setInterval("reinitIframe()", 200);

</script>