Did anyone see the previews for Friday the 13th ? Can anyone please explain to me what Jason is doing in this movie, and why does he have a hockey mask -_-. He's not supposed to be in the first movie and he's only supposed to get his mask in the third one.

It's actually an attempt to tie the first three together in some way.

I thought it was the first two.
Anyways, it's more than likely going to suck.
It's from the same production team (headed by Michael Bay) that brought us: The Hitcher and The Amityville Horror remakes.
They also did Texas Chainsaw Massacre's remake (and got the director from it to helm this project) though; and that was decent.
But the writers are from Freddy vs. Jason and The Messengers.

The reason the "mask" is being used is because corporate movie producers enjoy taking advantage of franchise symbols, and also enjoy making a dollar a dozen horror movie scripts.