Nikon D60. When viewing pics I get a section of the display that flashes on and off. I have no idea what's happened and I can't get back to viewing pics without the annoying flashing, it flashes black and white.

You're seeing blown-out highlights. These are the portions of your picture that have been overexposed so much that they've gone pure white and lost all detail. This is generally considered a bad thing, and the camera is warning you so. Of course, the camera doesn't know what effect you're trying for.

In general, the proper fix is to reduce the exposure by using exposure compensation to bring back the details. This risks losing details in the shadows as they go pure black, but that's generally considered not as bad. After all, we don't really expect to see things in the dark.

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