<br> and ::after or ::before

From this accepted answer : Which elements support the ::before and ::after pseudo-elements?

As you can read here http://www.w3.org/TR/CSS21/generate.html, :after only works on elements that have a (document tree) content. <input> has no content, as well as <img> or <br>.

Not funny, have you considered doing this with an image?

content: url(image.jpg)

This saying, i was designing something with ::before for a background-overlay on hover on an anchor.

I HAD to specify css content to empty {content=""} otherwize not displaying.

The :before and :after pseudo-elements are vaguely defined and poorly supported for elements like input. Your CSS code is not invalid, just not supported in browsers and not really defined in specs.

In an editor, which must be JavaScript-driven I presume, you can simply insert “↩” characters in the DOM (and remove them later if needed). Note, however, that “ ↩” has limited font support; a small image, scaled to the font size, might work better.