Configuring Joker.com to use your custom hostname
Step 1: Sign up for an account and register a domain at Joker.com, if you haven't already.
Step 2: Go to their Servicezone. It's where you'll edit all your account settings.

Step 3: Click the
icon to modify the DNS settings.

Step 4: Click the
beside the www.yourdomain.com to delete the existing www record.

Step 5: Click the Delete button to delete the existing record.

Step 6: You will be taken back to the screen before. This time click the button to edit the yourdomain.com without the www.
Leave the [empty] alone and add the SmugMug IP address 208.79.45.23 to the IP Address field. Click Save.

Step 7: In the Record Type: selector choose CNAME-Record (alias). Then click Add.

Step 8: In the (Sub-)Domain: field enter "www". Then enter "domains.smugmug.com into the Alias: field. Then click Save.

Step 9: This is what your screen should now look like. Click the Save button to save your changes.

Step 10: Type the entire domain name you're forwarding into the space provided by SmugMug in your control panel (ignore the guest password field; it's for something else).

Gotcha: They must be all lower-case or it won't work.
Don't add http:// or any / marks. Just type www.yourdomain.com (or photos.yourdomain.com, for example, if you set it up that way).
Step 8: Be patient. It takes 24-48 hours for DNS changes to take effect.
Let us know if you have troubles.