do u think it was necessary for Cedric Diggory to die off Goblet of Fire?

No, Cedric didn't have to die, but that was sort of the point, I thought. We saw just how terrible Voldemort was, killing an innocent who just happened to be in the wrong place at the wrong time.
The end of Goblet of Fire is really where the seris took a darker turn, I thought. It's where we start to realize exactly how horrible Voldemort and his followers are and how difficult it's going to be to defeat them.
If Cedric hadn't died, the only terrible things Voldemort would have done would have been in the past (well, at least in front of Harry). This way Harry, and the reader, really get to see how much of a bad guy he is and we want him gone just as much as Harry does.

Noooooo!!!!!!! I liked him!! And I'm not saying that because he eventually turned out to be Edward Culloen... I really liked him

YEAH!!!!!!!!!

It's important to Twi-hards.
Because , if Cedric didn't died in Goblet Of Fire , Robert Pattison wouldn't be in Twilight xD
Just Kidding. xD

yeah, I think it was necessary because is like the representation that the things are getting worst thean ahead. In the first books, we see Voldemort evil as something that is far away, as a memory, but when Voldemort returns, that memory is now present everywhere, so Cedric death is a warning that the next books are gonna be sader.

no way

yes i hate him hes a butt

CERTAINLY

As much as a Robert hater I am, I liked Cedric.
But, that's the thing, it showed you that you can grow so attached to a character and then the evils of Lord Voldemort can suck them away in no time!
Cedric's death was like a foreshadowing of the upcoming events. If it wasn't necessary for him to die, then apparently it wasn't necessary for anyone to. *shrug*

idont think Cedric should have did he was cool .and harry thought he was awesome

I think its cooler that he was killed!

well, it would have meant the whole Harry/Cho thing couldn't happen it OOP, but I wouldn't have minded them missing THAT out to me. Its the only part of HP that really annoys me. It was mostly just to prove how evil voldermort was, like someones already said. It was also to get rid of a character who would have had no real further part in the story alive. He had more impact dead.

Voldemort didn't want to have witnesses, if they had returned both alive, everybody at Hogwarts would believe Harry that Voldy had returned.

yea. i wish Harry would just have taken the blinkin cup & gone to Voldy & stuff.