Occasionally you may need to lock customers out of your site. This may be so you can work on a new UI or because something has gone wrong and you need to fix it before someone sees it. However, it would be good if you can still see the site so that you can check your own progress.

All you need to do to put magento into maintainance mode is to create a new file called

maintenance.flag

in the root.. and err that’s it

If you dont want to freeze yourself out you can edit index.php

around line 57 add

$ip = $_SERVER['REMOTE_ADDR'];

$allowed = array('xxx.xxx.xxx.xxx','xxx.xxx.xxx.xxx'); 

( where xxx.xxx.xxx.xxx is your ip addresses. )

then change the line

if (file_exists($maintenanceFile)) {
to
if (file_exists($maintenanceFile) && !in_array($ip, $allowed)) {

you can see the site and anyone else will get maintenance.