Matches the portion of an element that is selected by a user
::backdrop
Used to create a backdrop that hides the underlying document for an element in the top layer's stack
::placeholder
Allows you to style the placeholder text of a form element (Experimental)
::marker
For applying list-style attributes on a given element (Experimental)
::spelling-error
Represents a text segment which the browser has flagged as incorrectly spelled (Experimental)
::grammar-error
Represents a text segment which the browser has flagged as grammatically incorrect (Experimental)
Remarks
Sometimes you will see double colons (`::`) instead of just one (`:`). This is a way to separate pseudo-classes from pseudo-elements, but some older browsers like Internet Explorer 8 **only** supports single colon (`:`) for pseudo-elements.
One can use only one pseudo-element in a selector. It must appear after the simple selectors in the statement.
Pseudo-elements are not a part of the DOM, therefore are not targetable by `:hover` or other user events.