CSS-Lesson 4

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 capital '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 shown in CSS-Lesson 5.
  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

Note

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

To learn more about hexadecimal numbers click here.

Previous Lesson previous lesson next lesson Next Lesson