Anyhow, the question, posed by a new Christian with a Charismatic mother, is more or less "What is Blasphemy of the Holy Ghost?" Pentecostals will tell you that questioning "Speaking in Tongues" is blasphemy, and therefore an unpardonable sin, but how does this line up when compared with Scripture?
"But he that shall blaspheme against the Holy Ghost hath never forgiveness, but is in danger of eternal damnation:" (Mark 3:29)The scribes had just accused Jesus of casting out devils by the power of Satan, or saying that the Holy Ghost was the Devil. Basically calling the Holy Spirit Satan is the blasphemy that Jesus was talking about.
Under the circumstances, it was because Jesus was on earth, and was the physical manifestation of God. Therefore, saying something like this against Jesus (and the Holy Spirit) was blasphemy. However, that's the only time you see that showing up; nowhere else is Blaspheming the Holy Spirit even mentioned, so you can rest assured that this time is already past. Until the LORD comes back again, and sets up an entirely new government (Rev. 14:6-7), there won't be the ability to actually blaspheme the Holy Spirit as the scribes did.