Should I use single colons (:) or double colons (::) for before, after, first-letter and first-line pseudo-elements?

Question

From MDN:

The :: notation was introduced in CSS 3 in order to establish a discrimination between pseudo-classes and pseudo-elements. Br

Answer 1

I would would go for the single : People now a days should at least have somewhat of the latest browsers installed, so you have nothing to worry about.