A week ago, this public WordPress blog somehow become password-protected. When the Username and Password were not filled in, the blog came up perfectly…except for a few images.
How did that happen?
Turns out it was because the CSS style sheet was copied from the password-protected ancient Greek blog. The style sheet here was still trying to access background tiles from the password-protected blog!
Changing the background-image URLs to /wordpress/ fixed the problem immediately.
Probably not a problem most WordPress users will ever have to deal with.