There may be occasions when you will make your Joomla! website completely unavailable to visitors for a short time. There is a simple switch in the Administrator back-end that enables you to take your website offline very quickly. It can be returned to service at a later time just as easily.
To make your Joomla! website unavailable to visitors, replacing it with a simple message, do this:
Repeat the steps above and making sure the site offline switch is set to off.
Note that you can display a customized page during the time that your site is offline. To do so, create a file called "offline.php" and place the file in the home directory of your template. For example, if you are using the rhuk_milkyway template, the offline.php file would go in the directory "<Joomla! home>/teamplates/rhuk_milkyway/".
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You can limit access to certain resources of your website by password protecting the directories they are in.
To password protect directory with CPanel Hosting Control Panel:-
Login into your CPanel and click on Password Protect Directories
Once you click on Password Protect Directories, you will see a list of directories
Click on the directory that you wish to password protect
Fill in a Username and Password at the bottom of the page, and click Add / modify authorized user
Once user created successfully, just click “Go Back”
Now, Check the Directory requires a password to access via the web
Fill in Protected Resource Name, actually this is just the message that will show in the login window then, Highlight the user you just created from the Active Users list and click on Save button below the Protected Resource Name
To ensure you directory has been password protected, launch you browser and visit the folder, if browser prompt you to login, your directory has been protected by password!