So yesterday was my birthday and I got a canon EOS 1200d and I love it. But yesterday after I had taken a load of photos my screen started going black after taking every photo. When I use automatic setting it's fine but whenever I use manual and I've taken the photo the screen goes black and a red light shows. I have to turn it off and on again to make it normal. Also when I view the photo it comes out white. Help?
Manual mode lets you shoot yourself in the foot all you want. It sounds to me as if in M mode, your camera is set to have an extremely long shutter speed or is in bulb mode. In bulb mode you're holding the shutter open for an arbitrarily long period of time. The first shutter button press opens the shutter; a second one will close it.
My guess is that you meant viewfinder instead of screen going black, and that would be because the mirror has swung up and out of the way to let the light hit the sensor, but that means you can't see anything in the viewfinder because the mirror is no longer reflecting light from the lens up in to the pentaprism (and therefore, the eyepiece). When you turn the camera off, you interrupt the super-long exposure and end it.
The reason your playback is all white is because your super-long exposure has completely overexposed the shot. I'd say check the EXIF on the white images and see what the shutter speed was.
Live view mode(using the LCD screen to compose vs the viewfinder) will typically simulate the exposure of the image, although this can be turned off.
If you change settings in a manual mode to severely underexpose the image, live view will show you the very dark preview if you have exposure simulation on.
I am guessing that your camera is set to underexpose in one of the manual modes you are using. Try to correct for a proper exposure by raising ISO or aperture, or slowing the shutter speed and the LCD screen should lighten up to a visible amount.
Further, I am also curious if the "Exp. SIM" indicator on your screen is flashing or solid. I'm not sure exactly why your images would turn out white. That leads me to believe that you actually are overexposing the image, so you may want to try the inverse to expose less.