I'm currently designing a Maintainance countdown message. I think to create it as a pop-out modal window when the user logs-in and afterward place the countdown with a short header on a "sticky" position on the bottom of the screen / or under navigation. Does someone have any experience designing it? Do you believe that the pop-out modal window is appropriate in this case?
With a maintenance warning you could prevent the user from accessing the website with a modal popup. If the website is going to error whilst the maintenance is being carried out you may want to look into setting up a holding page.