I remember randomly finding a letter on a dead body of somebody,who probably fell off while trying to climb a mountain.
If I remember correct,I should take this letter to somebody,but I never found out to who in my first playthrough,and never found the place with this man in my other playthroughs.
So,if any of you happen to remember,where should I take this letter to ?
And where can I find it ?

I do believe the body is at the bottom of Dive Rock

You can find it on the corpse of http://www.uesp.net/wiki/Oblivion:Andre_Labouche. As tgl1992 said, he's at the bottom of Dive Rock.

Not sure why you'd take it to anyone, as the letter is to Andre in the first place, warning him that he shouldn't climb mountains given his natural clumsiness. The letter is from his daughter Fiona, who (best I can find) doesn't even exist in the game. Its apparent purpose seems to be explaining how he got where you find him- he's sort of similar to Morrowind's http://www.uesp.net/wiki/Morrowind:Tarhiel.

I think this is the man I was talking about..
Well,it seems my memory fooled me 'cause I thought there was a quest for him.
Anyway,thanks for replying.