This is the revision history for css units in <freenode.net:#perlbot>

factoid_idsubjectcopulapredicateauthornamespace
4711 css units is em [font height; i.e. 1em == font-size], ex [~ height of "x" in the font], px [pixels], in [inches], cm [centimeters], mm [millimeters], pt [points; 1 pt == 1/72 inches], pc [picas; 1 pica == 12 pt] perlbot <*:##NULL>