Absolute/Relative Units

NameCSSReal World
pixel 1px1/96"
point 1pt1/72"
millimetre1mm1/25.4"
pica 1pc1/12"
centimetre1cm1/2.54"
inch 1in1"
CSSDescription
1emfont size (default usually 12pt/16px)
1exex-height of font (=baseline to meanline)

CSS Length Shortcuts

Clockwise rule (from top, or north-west).

#Boxborder-radius
4t r b l↖ ↗ ↘ ↙
3t rl b ↖ ⤢ ↘
2tb rl ⤡ ⤢
1trbl

Note: border-radius allows horizontal / vertical axis declarations, where each of horizontal and vertical can have one to four lengths. e.g.:

20px 80px 40px / 10px 30px
 NW  NESW  SE    NWSE NESW
  horizontal      vertical

Media Queries

[See: CSS3-Media]