In many (all?) modern English translations of the Bible, if you flip to Mark 16, you’ll see some kind of note saying that Mark 16:9-20 may not be in the original version of Mark.
This note is driven by the study of Biblical manuscripts.
There are a lot of biblical manuscripts (handwritten copies of the Bible) out there, and they don’t always agree. This is actually a good thing, because it provides a wealth of material with checks and balances that help us more accurately determine what was in the original Bible text.
Most of the differences in copies are fairly easy to discern or completely inconsequential to the meaning of the text (e.g. “Christ Jesus” versus “Jesus Christ”). And I believe all of the differences (or at least the more major ones) are catalogued at the NET Bible, if anyone wants to see it for themselves.
Further, which brings us full circle, most modern translations of the Bible will include footnotes where there is a possible difference in some manuscripts. That’s what we see in Mark 16:9-20, as mentioned above.
Now, a nice assurance we have in studying Mark 16:9-20, is that the gist of everything there can be found elsewhere in the Bible. So no doctrine is hanging on whether Mark 16:9-20 was in the original or not.
For my part, I see fair evidence to support it being in the original, or at the very least inserted very early by the church (as a sort of true addendum, if you will, not as fabricating material or falsely attributing things to Mark). And along those lines, I recently read a 2011 article by John Tors that argues this very forcefully: Mark 16:9-20: A Response to CMI.
However, to be even-handed, I’d also recommend the reader checks out The NET Bible footnote on Mark 16:9-20. There he argues that it wasn’t in the original.
So, what do you think? Was Mark 16:9-10 in the original? Does it matter?