If you need to control the access to your Drupal website, so that only authorized people can see restricted sections or the entire site, the Drupal module Secure Site offers you a very easy and quick way to do so. Just download, install and enable the "Secure Site" module and there you go.
This module allows you to authenticate users with a browser-based password (HTTP Auth). You can restrict access to the site by role and choose to secure restricted pages or the entire site. If you choose to restrict the entire site, the website can only bee seen upon login. You may use the "Secure Site" module if you generally want that some sections or the entire site can only be seen by authorized people. This module is also very useful, if you want to restrict the access during the development or re-design of a website.