relative unitsem ems, the height of the element's font
ex x-height, ~ the height of the letter 'x'
px pixels, relative to canvas
absolute unitsin inches, 1in = 2.54cm
cm centimeters
mm millimeters
pt points, 1pt = 1/72 in
pc picas, 1pc = 12pt
#
The format of an RGB value in hexadecimal notation is a '#'
immediately followed by either three or six hexadecimal characters.
The three-digit RGB notation (#rgb) is converted into six-digit
form (#rrggbb) by replicating digits, not by adding zeros.
For example, #fb0 expands to #ffbb00. This makes sure that
white (#ffffff) can be specified with the short notation (#fff) and
removes any dependencies on the color depth of the display.
e.g.: #00FF00
rgb()
The format of an RGB value in the functional notation is 'rgb(' followed
by a comma-separated list of three numerical values (either three
integer values in the range of 0-255, or three percentage values in
the range of 0.0% to 100.0%) followed by ')'. Whitespace characters
are allowed around the numerical values.
e.g.: rgb(255,128,0)