How many and which values can/should be unitless in CSS

Question

I know two

• margin {0 auto}
• line-height: 1.5;

is there any other?

Answer 1

I don't really have an answer for your question, but I just wanted to say that I don't think you should ever leave off the units unless you're specifying a value of 0. It's easier to read and there's no guesswork (for both the browser and someone else who may be reading your CSS).

EDIT: Pulled this from a forum. They are the CSS properties that accept integer values for CSS 2.1 specifications:

• z-index
• font-weight
• line-height
• counter-reset
• counter-increment
• volume
• stress
• pitch-range
• richness

Answer 2

Every numerical value other than 0 should have a unit.

margin:0; //Good
margin:15; //Bad.  Do you want px, em, %, etc?

Answer 3

I am pretty sure I have had instances where leaving the value type off lead to display problems in other browsers. This is because they default to different types.
0 is 0 in any type.
Where 5px (pixels) can be a lot different then 5em (Width of the Current Fonts capital letter M).
As a best practice I say always use them. It's only a few more bytes of bandwidth.