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
How do people get to heaven?
Why do Muslims not eat pork?
God knowing in advance how I will use my free will means that god knows which events will lead to me being religious, and which to me being atheist. If God does exist, then doesn't his choice to set forth the latter mean he wanted me to be atheist?
By what criteria do you attribute veracity to your faith's sacred text(s,) and thus the basis of that faith? Is that criteria objective?
How can my mother enjoy Heaven, knowing that her atheist son will be tortured forever in the fires of Hell?
Muslim A Living Faith: My Quest for Peace, Harmony and Social Change Asghar Ali Engineer Muslim Welcome to Islam: A Step-by-Step Guide for New Muslims Mustafa Umar Muslim The Rights of Women in Islam Asghar Ali Engineer Muslim Islam in Contemporary World Asghar Ali Engineer Muslim Islam Fazlur Rahman Muslim The Prophet of Non-Violence: Spirit of Peace, Compassion & Universality in Islam Asghar Ali Engineer Muslim On Developing Theology of Peace in Islam Asghar Ali Engineer Muslim Islam: Religion, History, and Civilization Seyyed Hossein Nasr