Sati is a as cruel and inhumane observation in ancient India. In ancient Hindu texts, widows practiced Sati when they volunteerily burned themselves in pyre of their husband's cremation. On Historical accounts, the custom was forced on several widows in the name of Hinduism. Indian Government banned the practice in 1987.
Sati (Prevention) Act, 1987 is law enacted by Government of Rajasthan in 1987. It became a federal legislation with the enactment of The Commission of Sati (Prevention) Act, 1987 by Government of India in 1988. The Act seeks to prevent Sati practice or the voluntary or forced burning or burying alive of widows, and to prohibit glorification of this action through the observance of any ceremony, the participation in any procession, the creation of a financial trust, the construction of a temple, or any actions to commemorate or honor the memory of a widow who committed sati.
Ref : http://en.wikipedia.org/wiki/Sati_%28Prevention%29_Act,_1987
The term derived from Sati (aka Dakshayani) a Hindu godess, daughter of Prajapati Daksha and wife of Lord Shiva. She self-immolated herself in the event of her husband's humiliation by her father. She was appraised as "Good wife" in history thus the name carried to widows who burned themselves to follow their hunsbands to next world. In scriptures,
All incidents mentioned in Hindu texts refer to as voluntery act of "Good Wife". Over the time, it formed as expectation towards wives which led to utter murders of those who lost their husbands. Some acts followed even to extent of live burial of widows, drugging and tieing to husband's body as elaborate procautions to avoid escape for widows. In ancient times, Hindu Kings expanded their terriorries beyond seas into south east asia, the Sati practice was taken to those countries too.
Also, seems like a typical male dominated society belief and practice, where widower is never seen to follow his wife to next world. Widowers are allowed to marry again and live their lives happily after their wife's death. Sati was seen as act of "No life after hunsband's death" in earlier times. Several prominent Indian and Hindu visionaries, theologists and philosophers have described the practice as murder. Ex. According to Ram Mohan Roy, "All these instances are murders according to every shastra."
Though, it is mentioned in several incidents in texts and practiced widely in middle ages in India, Sati pracice is not a practice of Hinduism, but essentially blind or superstitious belief by people those who followed it.
I am sure, there is not a single Hindu today that agrees to Sati practice. More or less every hindu accepts that Sati was more of practice of past and not proud of it at any level.