Factual error: Vittoria Vetra "rolled down hills of edelweiss" as a child. Considering that edelweiss grows mainly on rocks and aren't very common she would have probably fallen to her death while rolling around in them.
Factual error: The storyline contains numerous ambigrams as supposed symbols of an ancient conspiratorial order, and even refers to some centuries-old, iron tools that are shaped in the form of ambigrams. However amibgrams were actually invented by Peter Newell (Lewis Carroll's illustrator) in 1893. For such a simple concept it is remarkable that no earlier examples are known, so careful searches have actually been made by art historians. However to date not a single example has turned up from earlier times.
Continuity mistake: In the beginning of the book, it is said that the jet goes 11,000 miles per hour, and that it took Langdon an hour to get to his destination. However, later, Langdon comments that he is 3,000 miles away from his home. So why did it take him an hour to get to CERN?