CSS Reference-Lesson 1

Each of the properties in CSS can have more than one value. In the following tables, the default value (indicated by '*') is the value of the property if the property is omitted.

CSS Units

Size

Size values can be split up into absolute and relative values. Some values (e.g. margins) can have negative values, preceded by '-'. Zero values do not require a unit.

Absolute values
Style abbreviation	Style meaning	Explanation
in	inch	= 2.54 cm
cm	centimetre
mm	millimetre
pt	point	= 1/72 inch
pc	pica	= 1/6 inch (12 points)
px	pixel	a dot on the screen

Relative values
Style abbreviation	Style meaning	Explanation
em	Height of 'M'	= 100%
ex	Height of lowercase 'x'
%	percentage	100% = 1em

Color values

The values for colours can be specified in a number of different ways:

1. as a 'name'. Various sources quote different numbers of colour names. The following seventeen fairly safe colours available are:

   Name	colour	Hexadecimal equivalent
   aqua		#00ffff
   black		#000000
   blue		#0000ff
   fuchsia		#ff00ff
   gray		#808080
   green		#008000
   lime		#00ff00
   maroon		#800000
   navy		#000080
   olive		#808000
   orange		#ffa500
   purple		#800080
   red		#ff0000
   silver		#c0c0c0
   teal		#008080
   white		#ffffff
   yellow		#ffff00

2. 'rgb(r,g,b)' where r, g, and b are decimal numbers between 0 and 255. This gives about seventeen million colours.
3. 'rgb(r%,g%,b%)' where r, g and b are decimal numbers between 0 and 100. This gives 1,030,301 colours
4. '#rgb' where r,g and b are hexadecimal numbers. This gives 4096 colours.
5. '#rrggbb' where rr, gg and bb are two-digit hexadecimal numbers. This gives about seventeen million colours.

Notes

The property 'background-color' can also have the value 'transparent'.

To learn more about hexadecimal numbers click here.