autofocus - Why doesn't auto-focus work with an all-white subject (like a wall)?

I am trying to compose a shot using my Nikon D60 and 18-55mm lens towards a white wall in a auto-focus mode.

It looks like I am not able to take the photo. I feel the camera is not able to find any subject to focus. The camera has a 3 point autofocus system. Is this a normal behavior of auto mode? If so, how can I compose a shot like this?

This is happening if I try to compose a shot with limited-color subjects — say, 2 color or single color subjects.

Any help would be helpful in my learning phase.

Thanks in advance.