The :blank pseudo-class builds upon the :empty pseudo-class. Like :empty, :blank will select elements that contain nothing at all, or contain only an HTML comment. But, :blank will also select elements that include whitespace, which :empty will not.
The :empty selector matches every element that has no children (including text nodes).The :empty CSS pseudo-class represents any element that has no children. Children can be either element nodes or text (including whitespace). Comments or processing instructions do not affect whether an element is considered empty.