What is the difference between :after and ::after?

Issue

It says the difference is that :after is CSS2, while ::after is CSS3. Are there any more important differences?

(I've tried Googling, but the colons seem to throw off the search)

Solution

Pseudo-elements were denoted with a single colon in CSS2, but have been changed in CSS3 "in order to establish a discrimination between pseudo-classes and pseudo-elements". For compatibility reasons a single colon is still allowed for the pseudo-elements defined in CSS 1 and CSS2.

CSS2

5.12.3 The :before and :after pseudo-elements

The ':before' and ':after' pseudo-elements can be used to insert generated content before or after an element's content.

CSS3

7. Pseudo-elements

[...]

A pseudo-element is made of two colons (::) followed by the name of the pseudo-element.

This :: notation is introduced by the current document in order to establish a discrimination between pseudo-classes and pseudo-elements. For compatibility with existing style sheets, user agents must also accept the previous one-colon notation for pseudo-elements introduced in CSS levels 1 and 2 (namely, :first-line, :first-letter, :before and :after). This compatibility is not allowed for the new pseudo-elements introduced in this specification.

Answered By - Zeta