On your site, you could give yourself a sort of an "Admin Control Panel" and have a boolean in a mySQL table, and when you want it to be under maitenence, you set it to "true" (via a checkbox in your ACP), otherwise, it's a "false".
Hello, my name is Matthew. I'm younger than all of you . I'm from Earth, particularly the USA, but sometimes I live on the net, mostly on Star Trek forums. I'm working on my PHP, I'm good a XHTML, and my site? Tutorials on web design. Stay tuned.