Bir de şöyle dene hocam.
<iframe src="iframe.php?url=http://siteadi.com" width="700" height="300" frameborder="0"></iframe>
iframe.php
<?php
if(isset($_GET['url'])){
$url = $_GET['url'];
$ch = curl_init();
$timeout = 5;
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $timeout);
$data = curl_exec($ch);
curl_close($ch);
echo $data;
}