Sometimes you may have to take your site offline, or during development you wish to keep the doors shut.

That default Joomla page that proclaims your site is closed is pretty drab.  What to do? The easy thing is to simply change the grammar via your Joomla backend. By default it is:
This site is down for maintenance. Please check back again soon.

You could even go so far as to add some basic html to this area, but that still pretty boring, and not very semantic. Why not do something fancier?

Fire up your favorite FTP client and navigate to you Joomla root directory.  Look for “offline.php”.  Make a copy of this file in case you foobar, and edit away.  Use basic html inside of it to spruce up your offline page.

Keep in mind this is a Joomla hack by definition, which means if you do a Joomla upgrade it will overwrite this file.  Make sure you keep a backup of it, or set your permissions so it is not able to be overwritten.