<div id="leamain">

       <iframe src="http://www.mamicode.com/#" marginheight="0" marginwidth="0" frameborder="0" scrolling="no" width="765" height=100% id="iframepage" name="iframepage" onl oad="iFrameHeight()" ></iframe>

<script type="text/javascript" language="javascript">

    function iFrameHeight() {

        var ifm= document.getElementById("iframepage");

        var subWeb = document.frames ? document.frames["iframepage"].document :

ifm.contentDocument;

            if(ifm != null && subWeb != null) {

            ifm.height = subWeb.body.scrollHeight;

            }

    }

</script> 

     </div>

iframe自适应高度(兼容IE 火狐 谷歌)