Well, to put it simply, this doesn't work:
<script>
alert("You are about to send email to the client! Do you want to proceed?");
var frame = document.getElementById("iframeMailer");
frame.src="qr.php";
</script>
When the user presses okay, the source of the iframe does not load.
It is by the way defined as follows:
<iframe src="example.php" height=130 width=50% frameBorder="0" seamless name="iframeMailer" id="iframeMailer"></iframe>