I am still building my shop, so I don't want any visitors at all while I am fiddling with it, nor do I want wrong content to be indexed. So I made it totally inaccessible for anyone but me:
.htaccess in your root directory:
Options +FollowSymLinks
RewriteEngine On
RewriteBase /
RewriteCond %{REMOTE_HOST} !^YOUR_IP_ADDRESS
RewriteCond %{REQUEST_URI} !^/503\.php [NC]
RewriteRule .* /503.php
and a 503.php in your rootdirectory:
<?php
ob_start();
header('HTTP/1.1 503 Service Temporarily Unavailable');
header('Status: 503 Service Temporarily Unavailable');
header('Retry-After: 86400');
header('X-Powered-By:');
?><!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>503 Service Temporarily Unavailable</title>
</head><body>
<h1>Service Temporarily Unavailable</h1>
<p>The server is temporarily unable to service your
request due to maintenance downtime or capacity
problems. Please try again later.</p>
</body></html>
The Retry-after: is value in seconds, adjust to own needs.