Unlisted Galleries
Unlisted galleries aren't visible on your SmugMug homepage and aren't included in search engines. You can give your friends a direct link to find your gallery, like http://smugmug.com/photos/2504559_f3ta9.
Similar to an unlisted phone number, there is a small (one in more-than-a-million) chance someone could just type in the right digits and stumble across your gallery. So, you may want to secure sensitive photos with a password.
Tip: Use SmugIslands to keep even public galleries or your entire site out of search engines.
Tell me how to make a gallery unlisted.
To make a gallery unlisted, make sure you're logged in. Navigate to the gallery you want to make unlisted and select customize gallery from the Gallery Tools Menu.
You'll see an option in the Security & Privacy sectioin that enables you to choose between public and unlisted.
Password-protected Galleries
Video guide: Password-protected galleries
Password-protected galleries require visitors to enter a password to see the photos inside. The galleries won't show up in SmugMug's search. Google can find them, but can't look inside.
If you choose a featured photo, the protected gallery graphic will be replaced with one of your thumbnail-sized photos.
Tell me how to password-protect a gallery.
When you're logged in, navigate to the gallery you want to secure and select customize gallery from the Gallery Tools Menu. You'll see a text box part way down the page that enables you to choose a password.
If you choose a password hint, your visitors will be prompted with it:

Tip: You can secure your entire SmugMug site with a password.
Give me more info on unlisted and password-protected galleries.
Q: I want to set one password for a group of galleries.
A: If you set the same password on multiple galleries, anyone who enters it will automatically be granted access to all galleries who share the identical password. Note that they must not DiFFEr In CaSe.
Q: Why doesn't my password-protected gallery require a password anymore?
A: For convenience, SmugMug remembers that you are authorized to visit a gallery once you have correctly entered the password. You can revisit the gallery, provided you do so on the same computer, for 24 hours without having to enter it again. Anyone who visits the gallery for the first time, however, will be asked for the password even if you're not.
Q: How can I share multiple unlisted galleries at once?
A: With ShareGroups.
Q: Ack! I forgot a gallery's password!
A: To see a password, simply follow the steps to set a password, above.