When you want to patch your site or just make some amends its a good idea to close the site so that your visitors don’t see the mess you make while patching 
You can easily do it using .htaccess file. I assume you know basics of Apache mod_rewrite so I’m not gonna explain each line.
Options +FollowSymLinks
RewriteEngine On
RewriteBase /
RewriteCond %{REMOTE_ADDR} !^192\.168\.1\.1$
RewriteCond %{REMOTE_ADDR} !^192\.168\.1\.2$
RewriteRule !holding_page.php|holding_page.jpg$ holding_page.php [R=307,L]
This line:
RewriteCond %{REMOTE_ADDR} !^192\.168\.1\.1$
specifies the IP address you want to let in to see your site. You can add as many IP addresses as you want.
Last line:
RewriteRule !holding_page.php|holding_page.jpg$ holding_page.php [R=307,L]
specifies two files that can be accessed by anyone (holding_page.php and holding_page.jpg). Everything else should be redirected to holding_page.php
We don’t want search engines to think we closed down our site. That’s why the flag 307 which means a temporary redirect.
