Cookie
You can use a basic cookie script to keep visitors from viewing certain parts of your site .
Gate Keeper
A somewhat more secure JavaScript password scheme.
Requires Netscape 2.0+ or Internet Explorer 3.0+.
Login and Password Script
This script asks for a username and a password.
Requires Netscape 2.0+ or Internet Explorer 3.0+.
Multiple Passwords Script
A script that requires multiple passwords to be entered.
Requires Netscape 2.0+ or Internet Explorer 3.0+.
Password Protect a Page
A simple unsecure password protection.
Requires Netscape 2.0+ or Internet Explorer 3.0+.
Elsewhere on About.com 
