|Ok well with the lack of information you have provided I'll just make a bunch of wild ass guesses|
You're using a very high compression level on the camera
You're using a very low resolution on the camera.
You have a crappy camera.
You're using an iPad 2 to take pictures.
You're shooting in low light levels and the shutter has to stay open longer causing motion blur.
You have it set on manual focus.
The lens is dirty
You're zoomed way in on the picture on your computer.
You're using a crappy picture viewer that doesn't handle anti-aliasing correctly.
It would really help if you provided all the info you can.