raised keyboard

My keyboard on my inspirion 5160 seems to be raised around the f7 to f9 keys and the 6,7, and 8 keys below it. When I press the keys the keys surrounding them move. It seems as if the keyboard is not secured down in that area. The keys surrounding the one I press are not pressed as well, they just move. Is this normal on a Dell laptop keyboard. I am not sure how else to explain this. The keys work fine, it is just like there is an air bubble under them.