Dynamic Iframe - Loop

// Use this if you believe the iframe may have dynamic content and could change size after it has completely loaded //
 
// Your Domain Name //
var parent_domain = "http://www.example.com/";
 
setInterval(function() { 
  var iframe_height = parseInt($('html').height());
  // Add Padding to insure nothing is creating a scroll bar //
  iframe_height += 30;
  
  // Pass Page Height back to main page //
  parent.postMessage( iframe_height, parent_domain ); 
}, 300 );

Dynamic Iframe - Main Page

// This script goes on the page that contains the iframe, not the page that is being iframed //

// Create Listener for iframe //
var eventMethod = window.addEventListener ? "addEventListener" : "attachEvent",
  eventer = window[eventMethod],
  messageEvent = eventMethod == "attachEvent" ? "onmessage" : "message";
 
// Listen for new iframe Height //
eventer(messageEvent,function(e) {
  $('iframe#dynamic_iframe_preview').css('height', e.data+'px');
},false);

Dynamic Iframe - Same Domain

$("iframe#dynamic_iframe_preview").load(function() {
  $("iframe#dynamic_iframe_preview").css('height', $("iframe#dynamic_iframe_preview").contents().find("html").height());
});

$(window).resize(function() {
  $("iframe#dynamic_iframe_preview").css('height', $("iframe#dynamic_iframe_preview").contents().find("html").height());
});

Dynamic Iframe - Single

// Use this script if you only want to update the iframe height once the iframe has fully loaded //
 
// Your Domain Name & iframe Height //
var parent_domain = "http://www.example.com/",
    iframe_height = parseInt($('html').height());
    
// Add Padding to insure nothing is creating a scroll bar //
iframe_height += 30;
 
// Pass Page Height back to main page //
parent.postMessage( iframe_height, parent_domain );