Textual conflicts and differences

Any serious student of the New Testament becomes aware of the discrepancies and differences in the ancient manuscripts.  When we looked at Mark 11, for example, the New International Version (NIV) has no verse 26, but includes footnotes that the phrase, "But if you do not forgive, neither will your Father who is in heaven forgive your sins" is not in the ancient manuscripts.

The New Testament was written in Greek, during the first century, on papyrus sheets that did not last long.  The letters that make up the New Testament were copied and recopied.  Our most ancient preserved versions date to the second or third centuries and these ancient versions (or copies of them) vary.  Most of the variations are slight, as the addition (or deletion) of a common phrase like that occurring in Mark 11:26.  Many of the deviations are a single word or a modification of a word, with no change in meaning.  However, some deviations are significant, as the end of Mark, where most ancient manuscripts stop suddenly at the end of Mark 16:8. (See this Wikipedia article on Mark 16.) The sudden ending at Mark 16:8 was surely not intended -- something has been lost -- but what?
Another famous manuscript difference occurs with John 7:53-8-11, which is absent in the most ancient manuscripts. On the other hand, John 21, occurring in the most ancient manuscripts, has some stylistic attributes that suggest to some scholars that it was a slightly later addition.  In the first epistle of John, I John 5:7-8, there is a late addition suddenly describing the Trinity; surely this was not in the original text and is not in the older manuscripts.

Preserved ancient New Testament manuscripts vary by age and region of preservation.  They have been extensibly studied and catalogued. Here, from Wikipedia, is a list of Bible verses in dispute, left out of most modern translations.  (As mentioned earlier, most of these are small minor changes between one manuscript and another, differences that have accumulated over time.  While one manuscript says "prayer and fasting", a commonly used phrase, another simply says "prayer.")

Evangelical tradition is to insist that God was active in creating an "inerrant original manuscript", through the Holy Spirit guiding the thoughts to the New Testament writer.  But due to the quick decay of the ancient writings, we do not have copies of those originals.  It is also possible that some letters had more than one "original".  When Paul wrote his letter to the Galatians, did he just write one copy and pass it around? Or did he write several copies?  Although papyrus was expensive, it is possible that Paul wrote several copies, each varying slightly.  Paul's letters read as if written naturally, on the spot, without drafts or outlines.  (In I Corinthians 1:13-17, for example, Paul starts to write that he "baptized no one" and then corrects himself.)

The situation is even move complicated with the more ancient Old Testament. Wikipedia has nice articles on Hebrew manuscripts (here and here) and on the Septuagint, the ancient Greek translation of the Old Testament.

My experience in the evangelical community suggests that some Christians focus on making claims about the Bible's inerrancy, in place of reading it.  If one believes (as I do) that the Bible is God's communication to humankind, then we should spend significant time reading it!  We will get back to that tomorrow.