Mormon scriptures speak of hell in two ways. The first is another name for spirit prison, a place for the spirits of people who have "died in their sins." The second is a more permanent place called Outer Darkness, reserved for the Devil, his angels, and those who have comitted the unpardonable sin. True to the Faith: A Gospel Reference, 2004, LDS Church. "Hell," p. 81; See also: Christian views on Hell (Latter-day Saints)
For example, a 2007 poll conducted by the Pew Research Center found that one in three Americans surveyed do not consider Mormons to be Christian. See for example ReligionNewsblog.com