After reading some of the claims listed on the site you linked to, I can conclude that there is an element of misinformation behind the content. And because there is so much of it, it would be unfair to expect me to sift through the material and provide a rebuttal for each claim. So I will direct you to a book which, if you sincerely desire the truth, should answer your question: http://islamicbookstore.com/b7626.html
If the Qur'an has never been altered, what about all the claims that it has listed here: http://www.answering-islam.org/Quran/Text/
The Muslim Perspective
If everything was created by God, was Buddha also created by God? Buddha actually denied the existence of a single being that dominates/governs the whole world. Did Buddha go to hell for denying his existence?
How can my mother enjoy Heaven, knowing that her atheist son will be tortured forever in the fires of Hell?
If God is the almighty designer and creator of the universe, and if God is a loving God who cares for His Creation, then why did he create life forms that have the necessity to consume eachother for their very survival?
If God doesn't change over time, can He know tensed facts? If not, how is He omniscient?
Do Muslims believe in reincarnation?
Answers: Muslim, Muslim
Muslim The Rights of Women in Islam Asghar Ali Engineer Muslim Welcome to Islam: A Step-by-Step Guide for New Muslims Mustafa Umar Muslim The Prophet of Non-Violence: Spirit of Peace, Compassion & Universality in Islam Asghar Ali Engineer Muslim Islam in Contemporary World Asghar Ali Engineer Muslim Islam vs. Islamism: The Dilemma of the Muslim World Asghar Ali Engineer Muslim Islam Fazlur Rahman Muslim On Developing Theology of Peace in Islam Asghar Ali Engineer Muslim Islam: Misgivings and History Asghar Ali Engineer