Screen is blank (MacBook)

An extremely rare event on Macs, but not impossible. This event, known as the Black Screen of Death can be removed using this sequence

1. Shut down the Mac and connect it to your MagSafe adapter and a wall outlet as usual
2. Hold down the Shift+Control+Option+Power button at the same time for a few seconds
3. Release all keys at the same time, then boot the Mac as usual

Also, consult this article for further help.

You may have reduced the brightness of your screen before and forgot to increase it. For instance, if your computer had to do some processing where the screen was not required (good to save energy). 

In that case, just turn the brightness up again. Check out the don't know how to make the screen brighter solutions to learn how to increase it.

Maybe your screen is black because your device is not turned on, or maybe you have accidentally turned it off.

If you are using a computer and it doesn't turn on, check out the solutions to the computer doesn't turn on issue.

The power outlet used by the device could be malfunctioned and that's why you are unable to power it up your device. Try plugging the device in another outlet nearby, or replace the existing one.

If you are not sure how to fix the power outlet, don't put your life at risk and call an experienced electrician.

Nowadays, you can reach most manufacturers or retailers directly via live chat, email, or direct call, and have your faulty device replaced.

Check their websites for more information regarding how to contact them.