In the margin of my Bible, this note accompanies Mark 16:9: "Some of the
oldest manuscripts do not contain Mark 16:9-20."
It refers to the two Alexandian texts, Codex Sinaiticus and Codex Vaticanus.
In the Codex Vaticanus, the copyist was aware of the verses, for he normally
began the next book at the top of the next column, except at the end of Mark
where there is a blank column between the end of Mark and the next book. It
is the only blank column in the text.
The Codex Sinaiticus is different. In the Codex Sinaiticus the verses were
removed, pumiced out, but not completely as you can see for yourself at:
http://www.csntm.org/Manuscripts/GA%2001/GA01_029a.jpg
To get to the page, search Codex Sinaiticus for Mark 16:8, the verse before
the erasure.