Units of Measure

Length Units

Length indicates a number followed by a unit of measure: 24px.

The number can be an integer or a decimal fraction, and can be preceded by + or -.

Units can be absolute or relative:

Absolute: mm, cm, in, pt, pc (millimeters, centimeters, inches, points, picas)

Relative: em, ex, px (the element's font height, the element's x-height, pixels)

Font size may be defined in points, pixels, inches, or centimeters (pt, px, in, cm) or as a percentage.

absolute-size can be: xx-small, x-small, small, medium, large, x-large, xx-large.

relative-size can be: larger, smaller.

Percentage Units

percentage indicates a number followed by a % sign: 50%.

In the text-indent, margin, padding, and width properties, percentage values are relative to the width of the parent element.

In the font-size property, percentage values are relative to the font size of the parent element.

In color values, percentages can be used to express RGB values.

Color Units

color can represent either color-name or rgb values, as defined below:

color-name can be: aqua, black, blue, fuchsia, gray, green, lime, maroon, navy, olive, purple, red, silver, teal, white, yellow

rgb can be: #<hex><hex><hex>, rgb(<number>, <number>, <number>), rgb(<percentage>,<percentage>,<percentage>), rgba(<number>, <number>, <number>,<decimal>)

Hope this Helps, Happy Web Building!