Nope, character death is not something you have to warn about - rules wise. Esp if it isn't Buffy or Spike.

-- That was me being a mod, as for personal opinion, I prefer to be warned about a character death if it is going to have a strong emotional impact on me. Especially if it happens toward the end of the story and whatever grief one may experience won't be resolved by the end of the fic. (Yes, I know, grieving for a fictional character, makes me sound a bit daft, can't think of a better word though.) If it happens early on, or with enough stuff coming afterward that the impact is dampened by the time the story is finished, I don't mind so much. It's up to the author whether they want to warn about CD though, I know quite a few people consider it a spoiler and prefer not to use it.

Ugh, sorry if this is slightly incoherent. Am talking to my mom on YM while writing this, and switching languages like this is not something I'm good at.

ETA: Seeing Always_jbj's comment, I should probably add that I'm a huge spoiler whore; I frequently read the endings of books or fics before the rest. As far as I can tell, that's a rather unusual mindset, so you should probably mostly ignore my opinion. ;-)