Flashing photos on a Nikon camera

You're seeing blown-out highlights. Those are the portions of your photos that have been so badly overexposed that they've gone pure white, losing all detail. This is generally considered a bad thing and thus the camera is warning you about it. The proper fix is to reduce exposure so as to bring back highlight details. This risks losing details in the shadows as they go pure black, but that is generally considered not as bad as losing highlight details since we don't expect to see things in the dark. However, the camera doesn't know what effect you're striving for. Sometimes blown-out highlights are perfectly acceptable, thus the camera merely warns you that it's happening.

That was the long answer. The short answer is to press up/down on the multiselector to cycle through different views of your pictures.