CSS difference between 0 and 0em

Question

Is there any difference between

margin: 0;

and

margin: 0em;

I didn't notice anything, but my teacher keeps telling me that it's not the same.

Answer 1

The file is bigger with 0em.

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The way to prove to your professor that there is no difference is to set something to 0 and something else to 0em and inspect the DOM with Firebug or a similar tool. If I recall correctly, you'll see that both are now 0. So the only difference is in the source. (But it's been a while since I checked. I might be thinking of getting and setting styles from jQuery. So check it out before you take my word.)

Answer 2

There's no difference when the value is 0. If it were 1 and 1em, yes, there's a difference, but 0 is 0, no matter the unit.