Password protection for a page, a post or the whole site

Keep a staff area, a launch or a client preview private with a password, for one page, one post or the whole site.

Whole site: Site Settings > Privacy. Visitors see a password form before any page.
One page: Pages > page actions > Page settings > Password.
One post: in the post editor, switch on password protection and set the password.

Changing the password signs out everyone who unlocked it with the old one. Protected pages are left out of the sitemap.

Where: Open Privacy (sign in first)