Hey,
Doing as Mike suggested will stop ALL traffic from viewing your site. Correct me if I'm wrong, but you wanted to let people sign up to view the site, so you'll need at least 1 page to have a sign up form on it?
Just setup your homepage as your signup page that everyone can access, and then setup your website within another directory such as 'site', so it would live at
www.yoursite.com/site (and within the directory structure, it would live at public_html/site). Then you can password protect the 'site' directory.
There are many ways to skin a cat and this is just one
