Giving a `<span>` a negative vertical margin

Question

Why can't a <span> have a negative vertical margin or padding?

If I set it to display: block, it still doesn't work.

Answer 1

From the CSS 2.1 spec:

8.3 Margin properties: 'margin-top', 'margin-right', 'margin-bottom', 'margin-left', and 'margin'

Margin properties specify the width of the margin area of a box. The 'margin' shorthand property sets the margin for all four sides while the other margin properties only set their respective side. These properties apply to all elements, but vertical margins will not have any effect on non-replaced inline elements.

<span> is, by default, a non-replaced inline element.

Also

8.4 Padding properties: 'padding-top', 'padding-right', 'padding-bottom', 'padding-left', and 'padding'

...

Unlike margin properties, values for padding values cannot be negative.