If you have your Joomla site set to allow new user registrations, you should add a layer of protection against registration bot abuse by setting the New User Account Activation Level in Joomla to something higher than "none." How to set the new user account activation level in Joomla is what today's Maintenance Monday is all about.
Eventually you may need to put your Joomla site offline. Before you reach that point, snazz up the "Site is Offline" page and message so your site visitors aren't totally disappointed. How to customize your "Site is Offline" message is what today's Maintenance Monday is all about.
Stuff happens that can cause your web site to go down even when you aren't working on it. To help alert you to these times when your site is down, set up a monitor that automatically tells you there is a problem. How to setup free UpTime Robot site monitors is what today's Maintenance Monday is all about.
You may be really great at picking secure passwords for your Joomla account, but are the other people creating accounts on your site as careful? You can set up your Joomla site to require users to create passwords that are hard to guess or hack. How to change the password strength setting in Joomla is what today's Maintenance Monday is all about.
If your Super Admin username is something easily guessed, you have already given away half of the login info required for a hacker to have his or her way with your site. This is especially true if your Super Admin username is "admin" - a well known default username from a number of Joomla version ago. How to change your Super Admin username to something other than "Admin" (or something else) is what today's Maintenance Monday is all about.