<iframe name="my_iframe" id="mainframe" marginheight="0" marginwidth="0" frameborder="0" scrolling="no" width="100%" height="100%" src=""></iframe>

var browserVersion = window.navigator.userAgent.toUpperCase();
var isOpera = browserVersion.indexOf("OPERA") > -1 ? true : false;
var isFireFox = browserVersion.indexOf("FIREFOX") > -1 ? true : false;
var isChrome = browserVersion.indexOf("CHROME") > -1 ? true : false;
var isSafari = browserVersion.indexOf("SAFARI") > -1 ? true : false;
var isIE = (!!window.ActiveXObject || "ActiveXObject" in window);
var isIE9More = (! -[1, ] == false);
function reinitIframe(iframeId, minHeight) {
  try {
    var iframe = document.getElementById(iframeId);
    var bHeight = 0;
    if (isChrome == false && isSafari == false)
      bHeight = iframe.contentWindow.document.body.scrollHeight;
    var dHeight = 0;
    if (isFireFox == true)
      dHeight = iframe.contentWindow.document.documentElement.offsetHeight + 2;
    else if (isIE == false && isOpera == false)
      dHeight = iframe.contentWindow.document.documentElement.scrollHeight;
    else if (isIE == true && isIE9More) {//ie9+
      var heightDeviation = bHeight - eval("window.IE9MoreRealHeight" + iframeId);
      if (heightDeviation == 0) {
        bHeight += 3;
      } else if (heightDeviation != 3) {
        eval("window.IE9MoreRealHeight" + iframeId + "=" + bHeight);
        bHeight += 3;
      }
    }
    else//ie[6-8]、OPERA
      bHeight += 3;
    var height = Math.max(bHeight, dHeight);
    if (height < minHeight) height = minHeight;
    iframe.style.height = height + "px";
  } catch (ex) { }
}
function startInit(iframeId, minHeight) {
  eval("window.IE9MoreRealHeight" + iframeId + "=0");
  window.setInterval("reinitIframe('" + iframeId + "'," + minHeight + ")", 100);
}