Normal Joomla operation requires a valid user to enter their...
Normal Joomla operation requires a valid user to enter their username and password to get past the offline template page. Logging in prevents testing of guest functionality on your site. So your choice to take your site offline for development or testing actually prevents an entire segment of test cases - the guests (unregistered visitors)!
An administrator can set the site in offline mode inside Joomla Global Configuration, and enable this plugin to grant login-free access to the site. Browse the site as a guest (or login) - while still in offline mode.
Download Offline from the RicheyWeb download page.
This page will remain unlinked, as the link may change in the future. Visit http://www.richeyweb.com and use the search feature - search for "Offline".
In Joomla /administrator, go to the "Extensions" menu, the "Manage" sub-menu, and the "Install" sub-menu.
Select the "Upload Package File" tab
Press the "Choose File" button to browse your system and locate the plugin file you downloaded
Press the "Upload & Install" button
At this point, the extension is installed but not enabled. You can find the plugin by going to the Extensions menu and selecting "Plugins". When in the plugin manager, search for "Offline".
Enable the plugin
Set a key
Copy the URL displayed above the key and paste it into your browser address bar.
Press the "Select" button next to IP Whitelist, and add any IPv4/IPv6 addresses or IPv4 CIDR defined networks that you wish to automatically bypass the key requirement. IPv6 CIDR is possible if your server has PHP-GMP installed.
If you are not familiar with CIDR netmasks, you can review the details in this Wikipedia article