bugs about css

Question

for example:
margin:0px 0px 0px 0px;

It should be:
margin:0 0 0 0;
because all value no need unit when it is 0;
more:
It can be as:
margin:0 0;
or margin:0;

Answer 1

They do the exact same thing. They are both compatible in all browsers, it interprets both as 0, say go with whatever is more readable for you.

Answer 2

t should be:
margin:0 0 0 0;
because all value no need unit when it is 0;