This is the code that I'm working with:

<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<style>body,table,input,select,textarea,div {font-family:tahoma;font-size:8pt}</style>
<form name="login">
<p dir="rtl" align="left">
<input type="text" name="js4ir" size="14">
<input type="button" value="Go" onClick="Login(this.form)">
<script language="JavaScript" link="">
function Login(form) {
var js4ir = form.js4ir.value;
if (js4ir) {
var site = "http://" + js4ir; window.location = site;}
else {alert("Please enter your adress");}}
<br><a target="_blank" href="">
<span style="text-decoration: none"></span></a>

I'm having trouble editing it so that it will open the web pages in an iframe. How would I do this?