Coloured lines running down the screen!?

I recieved a 50" LG as a gift because there were these black hairlines running down the screen, 4 of them, i took it home, turned it on and they were gone.bonus,....now, 1 year on, these semi-transparent lines are running vertically on the screen, there was one, then two, now 3. What is this problem and how do i fix it?, Thanks