What is happening to my laptop screen?

[Rufus]

As you can see in the photo, the whole screen has darkened apart from that small area you can see at the bottom of the screen. Since the picture was taken, this area has grown. there is a small possibility that a tiny droplet of water got into the gap between white plastic and screen - is this the cause and is there a solution?

[TheEnd]

yep, that's water damage.
i don't think it'll be cleanable, as it will tend to leave marks, but try warning it up a bit to dry out, an airing cupboard for example