Codex Vaticanus originally contained a complete copy of the Septuagint and the New Testament, but pages 1519-1536 containing Hebrews 9:14 through Revelation were lost and replaced by a 15th century minuscule supplement (no. 1957).
Codex Vaticanus has been housed in the Vatican Library (founded by Pope Nicholas V in 1448) for as long as it has been known, appearing in its earliest catalog of 1475.
Its previous history is unknown, but there has been speculation that it had previously been in the possession of Cardinal Bessarion because the minuscule supplement has a text similar to one of Bessarion's manuscripts. T.C. Skeat, a paleographer at the British Museum, has argued that Codex Vaticanus was among the 50 Bibles that the Emperor Constantine I ordered Eusebius of Caesarea to produce.
Codex Vaticanus is a leading member of the Alexandrian text-type and was heavily used by Westcott and Hort in their edition of the Greek New Testatment (1881).
In 1995 double dots ("umlauts") have been discovered in the margin of the new testament, which seem to indicate positions of textual variants. The date of these is disputed among scholars. Have a look at: http://www-user.uni-bremen.de/~wie/Vaticanus/index.html for details.