font color - a single character value specifying
a valid color (e.g. "#000000" or "black").
font.size
font size (in point) - 0 or positive integer value.
font.weight
single character value specifying font weight
(expected value is normal or bold).
font.style
single character value specifying font style
(expected value is normal or italic).
underlined
single logical value specifying if the font is underlined.
font.family
single character value specifying font name (it has to be
an existing font in the OS).
vertical.align
single character value specifying font vertical alignments.
Expected value is one of the following : default 'baseline'
or 'subscript' or 'superscript'
shading.color
shading color - a single character value specifying
a valid color (e.g. "#000000" or "black").