<iframe id="ifm1" runat="server" src="/comment/page1?id=@productId" width="100%" height="100%"  frameborder="0" border="0" marginwidth="0" marginheight="0" scrolling="no" allowtransparency="no" ></iframe>

   function reinitIframe() {

        var iframe = document.getElementById("ifm1");

        try {

            iframe.height = iframe.contentWindow.document.documentElement.scrollHeight;

        } catch (ex) { }

    }