Currently, the none value of the content property says that:
On pseudo-elements it inhibits the creation of the pseudo-element as if it had display: none.
This is not respected universally in all three major browsers for all pseudo-elements. For example:
<!DOCTYPE html> <style> dialog::backdrop { background-color: green; content: none; } </style> <dialog id="dialog"></dialog> <script> dialog.showModal(); </script> The green backdrop is visible in Firefox, Chrome and Safari.
I don't have time to test all the other pseudo-elements, but I'd assume that this is not just a problem with ::backdrop.