jQuery changing contents of an iFrame

If you want to update the iframe content using html then you should first find the body element inside the iframe and then append the required markup.

$(document).ready(function() {
    $('#prev').contents().find('body').html('<div> blah </div>');
});

Working demo - http://jsfiddle.net/ShankarSangoli/a7r9L/

I have created a PHP script that can get all the contents from the other website, and most important part is you can easily apply your custom jQuery to that external content. Please refer to the following script that can get all the contents from the other website and then you can apply your cusom jQuery/JS as well. This content can be used anywhere, inside any element or any page.

<div id='myframe'>

  <?php 
   /* 
    Use below function to display final HTML inside this div
   */

   //Display Frame
   echo displayFrame(); 
  ?>

</div>

<?php

/* 
    Function to display frame from another domain 
*/

function displayFrame()
{
    $webUrl = 'http://[external-web-domain.com]/';

    //Get HTML from the URL
    $content = file_get_contents($webUrl);

    //Add custom JS to returned HTML content
    $customJS = "
    <script>

      /* Here I am writing a sample jQuery to hide the navigation menu
         You can write your own jQuery for this content
      */
      //Hide Navigation bar
      jQuery(\".navbar.navbar-default\").hide();

    </script>";

    //Append Custom JS with HTML
    $html = $content . $customJS;

    //Return customized HTML
    return $html;
}