DIRTY
Your photo(s) had blemishes on them.

If the image is from a digital single-lens reflex camera (DSLR), these blemishes may be dust spots ("dust donuts"), which are often difficult to see. They are caused by dust on the CCD/CMOS sensor of your camera. DSLR are very sensitive to the problem, because of the removable lens. To minimize this problem, always hold your camera with the lens pointing down, when changing the lens. If your camera sensor is very dirty, you will need to have it cleaned. There are ways to do this yourself, but this is not without risk. You can also ask your camera dealer.

If the image is from a regular digital camera, the blemishes are probably caused by dirt on the lens. Please clean your lens regularly.

If the image is from a scanner, the blemishes may be dust, dirt or scratches. These may have been in or on the scanner itself, or on the photo, negative or slide. Always clean negatives and slides very carefully with a high-quality brush before scanning them, but be careful not to cause any damage. If this does not help, the scanner itself may be dirty. For a flatbed scanner, use microfiber cloth and window cleaner or another appropriate glass-cleaning product to clean the scan bed. For film/slide scanners, try using compressed air to blow out any dust. Scratches cannot be cleaned, but will need to be repaired with the help of image editing software. Depending on the location and size of the scratch, this may be a very difficult task.

You might also receive this rejection, because your photo had some "hot pixels" in it. These broken pixels appear in photos taken with all kinds of digital cameras and are often only visible on relatively dark shots with a long exposure time (e.g. night shots). They will usually appear as tiny red dots.

A simple way to remove dustspots using Photoshop can be done as follows:

Create a duplicate layer: Layer-> Duplicate layer.
Press F7 to bring up the layers window, this will appear to the right of your screen.
Select the new "Background Copy" by clicking on the name.
Now equalize the image, (3.0) Filter-> Adjustments->Equalise,(2.0) Image->Adjustments->Equalize
Select the "Background layer" instead of the "Background Copy" layer. You will still see the equalised image, but all changes are being made on the original image.
Select heal tool, you will need to set the heal tool so press 'Alt' and click, (left click) near the spot in question, do this for each spot. Photoshop CS2 has a "spot healing brush tool" which allows removing dustspots by a single mouseclick.
Heal the dust spots on the image. You will not see the spots disappear, but they do disappear on the original image so remember which ones you did already. If you healed all dust spots continue to the next step.
You can now delete the "Background Copy" layer. Select the "Background Copy" by clicking on it and then delete, Layer->Delete Layer
You should now see the original image, which if the above steps are performed correctly is free of dustspots.

Photo copyright © Thierry Deutsch

broken pixel - Photo copyright © Thierry Deutsch

What initially looks like a perfectly dustfree photo... / ... might prove to be anything but ... (also note the broken pixel in the upper left part <-> white dot) - Photo copyright © Thierry Deutsch

Equalized picture with unrecognizable dust spot / Dust spot apparent on non-equalized picture - Photo copyright © Thierry Deutsch

Always double-check your photos by equalizing them to be sure that no spots of any kind are present anymore. Nothing's more frustrating for the photographer and the screener than the rejection of a shot for such an easy to avoid reason. Sometimes though equalizing the picture can render some areas so dark that dust spots disappear completely in them (see example above).

If you´re shooting digital, watch for broken pixels, especially on night shots!