When your website is being worked on you could show an under maintenance message on every page with little to no effort just like the big wigs websites, Like the under maintenance messages that Youtube shows when there site is under for maintenance as an example.

Manage your Under Maintenance Messages and Update your Terms and Agreements with just a Few Clicks.

Once you install the script you can then Login to the Admin Panel Area and be able to Change your Login Information and Get the Code to Paste on your Website so that you can begin to use the Script with ease.