You can use JavaScript window.location to redirect a visitor to a required page. You may have seen this feature used by sites with full page ads, or to redirect visitors to the site's new domain name. You can add also a timer to the script that will allow

gistfile1.js

<script type="text/javascript">
/* Source: http://www.apphp.com/index.php?snippet=php-get-remote-ip-address */
var count = 6;
var redirect = "http://www.apphp.com";
function countDown(){
    var timer = document.getElementById("timer");
    if(count > 0){
        count--;
        timer.innerHTML = "This page will redirect in "+count+" seconds.";
        setTimeout("countDown()", 1000);
    }else{
        window.location.href = redirect;
    }
}
 15.
</script>
Our webpage has beed moved. Please update your bookmarks for the new site.
<br>
<span id="timer">
<script type="text/javascript">countDown();</script>

</span>