  We determine the frequency of the Yb I $^1S_0 - ^1P_1$ transition at 399 nm
using an optical frequency comb. Although this transition was measured
previously using an optical transfer cavity [D. Das et al., Phys. Rev. A 72,
032506 (2005)], recent work has uncovered significant errors in that method. We
compare our result of 751 526 533.49 $\pm$ 0.33 MHz for the Yb-174 isotope with
those from the literature and discuss observed differences. We verify the
correctness of our method by measuring the frequencies of well-known
transitions in Rb and Cs, and by demonstrating proper control of systematic
errors in both laser metrology and atomic spectroscopy. We also demonstrate the
effect of quantum interference due to hyperfine structure in a divalent atomic
system and present isotope shift measurements for all stable isotopes.
