Coloured Vertical Lines on Screen I dropped my macbook air and the screen is like this since.



Does anyone know what exactly happened to it? Is it hardware or software?
Diagnosing Hardware vs Software Problem
As stated in my comment, to diagnose if it is a software or hardware issue (most likely hardware), try connecting the Macbook to an external monitor. If the external monitor displays the screen, then your Macbook must have the problem (It's a hardware issue). If both the external monitor and the Macbook pro still won't display anything, it is a software issue.
The Problem
The display probably went bad. You can try pressing the screen at certain points and see if it gets restored (This won't fix anything).
Resetting the NVRAM/PRAM- Last Chance
One last thing to try is resetting the NVRAM/PRAM (I read this on a post once, I don't think it will work but it cannot hurt to try):

Shut down your Mac.
Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
Turn on the computer.
Press and hold the Command (⌘)-Option-P-R keys before the gray screen appears.
Hold the keys down until the computer restarts and you hear the startup sound for the second time.
Release the keys.

Related Links
Apple Discussion

I have the same problem. Resetting PRAM is the only way to boot and it
only works on that boot. If the system is off for more than maybe 5
minutes, I'm back to the vertical colored lines. Multiple reboots in a
short amount of time are ok.

Does this happen for you too when you reset the PRAM?
Take it to the Genius Bar at the Apple Store (hopefully you have AppleCare or under 1 year limited warranty).