Several times I had the problem of showing the website to a client while I needed to have the site off-line.
Site lock solves the problem. The site is off-line but I can assign a specific username and passwod to the client and he can see how the site while it is still off-line.
I was unable to get it working at first as the template was created with Artisteer...
Make sure you add a line of code in the template you are working with...
in file /templates/templatename/html/com_content/article/default.php