<p>To make your Joomla! website unavailable to visitors, replacing it with a simple message, do this:</p>
<ol>
<li>Log in to the Administrator back-end.</li>
<li>Click on the <strong>Global Configuration</strong> button in the main Control Panel or <strong>System → Global Configuration</strong> in Joomla 3.x.</li>
<li>There are so many configuration options that they need to be divided into separate groups or tabs. The <strong>Site</strong> tab, it should be the default first view displayed, if not click on the tab.</li>
<li>Find where it says <strong>Site Offline</strong> and click the <strong>Yes</strong> button in Joomla 3.x.</li>
<li><strong>Optional:</strong> Change the <strong>Offline Message</strong> to give your visitors some explanation about why your website is unavailable.</li>
<li>Click the <strong>Save</strong> toolbar button to implement the new settings:
<ul>
<li>The <strong>Save</strong> toolbar button will save your changes and but leave you in Global Configuration.</li>
<li>The <strong>Save and Close</strong> button will save your changes and return you to the Administrator Control Panel.</li>
</ul>
</li>
<li>You should see a message confirming the settings have been changed.</li>
</ol>