Using the standard theme
The C for the Christening usually appears to the left of the B for Birth.
The B (birth) and D (death) reverse out nicely when hovered over ... black->red and transparent->pale yellow
But the C (christening), M (marriage), O (occupation) become white on pale yellow which is effectively invisible. The "white" seems to be hard coded as I can't find a setting for it in the style.css
Also the O (occupation) gives the OCCU DATE and PLAC but not the actual occupation.