Why are my pictures on my DSLR showing up black?

I'm using a Nikon D200 and recently my photos are black when I look at them. It hasn't done this before. What can I do to fix this?

Thanks!

Added (1). I don't know what that means… There are too many buttons!

Are you shooting on manual without checking your meter?

Black you say mmm

There are a few options, first of all indeed what setting it is in. Fully Automatic, Program Mode, Aperture Mode, Speed Mode

But lets first do something simple, remove the lens and switch the dial to S, set an exposure time of 2 seconds and turn the camera so you look into it down to the mirror. Press the shutter. If it is good the mirror flips up and you see the sensor exposed. If it doesn't flips up the sensor gets no light so it will be a dark nothing.

So first make sure the mirror flips up, that is by taking a picture without a lens on it and being on the front so you can see the mirror move. Or not

If the mirror moves then move the mode dial to [mmm that is the Mode Button on the D200] I guess called it the mode BUTTON is better.well move to the P mode for program. Put the lens on it and switch it off and on so the lens gets settled in and voila shoot again.

Now see if you get an image.

Black means gross underexposure.of the image

Look on page 68 of your user manual to see how to use the cameras light meter.

The button you need to concern yourself with is the shutter release. The two thumb wheels adjust the lens aperture and shutter speed. Use the light meter to assure near perfect exposures

Here is where you can practice balancing ISO, shutter speed and lens aperture.

http://camerasim.com/camera-simulator/

Have you considered taking a class in photography? That would be an excellent start.