http://www.nikonchat.com/d90-nikon-problems/

FX lens Can be used with a DX camera or bullet is going to happen?
I would buy a Nikon 70mm to 300mm zoom lens but not a DX lens. Will this cause a problem because I own a Nikon D90, and is a DX format camera.
It is the opposite. An FX lens is designed for a larger sensor and provides a larger image to the camera. A DX lens is designed for a smaller DX sensor and provides a smaller image. A DX lens on a FX body will vignetting. An FX lens on a DX body is 100% compatible. BTW, I use older full frame of my film Nikon lenses 35mm SLR days on my DX D200 without any problem. If you use a DX lens on a Nikon FX camera, the camera automatically switches to DX mode. Of course, you lose resolution, but you still find DX lenses to be a great option in the camera bag.
D90 – Hamburg St. Pauli at Night