Struggling to obtain password protection for a single page?

The normaly .htaccess routine that would allow you to setup password protection for a page:

AuthUserFile "/path-to-password-file/"
AuthName "Restricted Access"
AuthType Basic
<Files file-name>
Require valid-user
</Files>

Doesn't work because of Drupal's rewrite rules.  Here's how to overcome the issue.

Creating the 401.shtml page

Add a page named "401.shtml" in your root.  Typically you'll want the page to be in html format (ie. with html and body tags at a minimum), and add a message such as "Access Denied," as this page will get loaded if the user cancels out the password dialog box, or if they fail to enter valid login information.  Typically, a 401 page contains the following:

Authorization Required

This server could not verify that you are authorized to access the document requested. Either you supplied the wrong credentials (e.g., bad password), or your browser doesn't understand how to supply the credentials required.

Once you have created the above page you can add the above .htaccess routine to your .htaccess file.  The only remaining step is adding a user:password combination (the password is an Apache modified MD5 encryption, or generated using the system's crypt() command) to your .htpasswd file and storing this file above your document root.