An asterisk (*) is the universal selector for CSS. It matches a single element of any type. Omitting the asterisk with simple selectors has the same effect. For instance, *.warning and .warning are considered equal.
The ::-moz-placeholderpseudo-element represents any form element displaying placeholder text. This allows web developers and theme designers to customize the appearance of placeholder text, which is a light grey color by default. This may not work well if you've changed the background color of your form fields to be a similar color, for example, so you can use this pseudo-element to change the placeholder text color.
The :-moz-full-screen-ancestorCSSpseudo-class applies to all ancestors of the full-screen element, except containing frames in parent documents, which are the full-screen element in their own documents. However, those elements' ancestors have this class applied to them.
The :-moz-loadingCSSpseudo-class matches elements, which can't be displayed, because they have not started loading, such as images that haven't started to arrive yet. Note that images that are in the process of loading are not matched by this pseudo-class.
The :-moz-locale-dir(ltr)CSSpseudo-class matches an element if the user interface is being displayed left-to-right. This is determined by the preference intl.uidirection.locale (where locale is the current locale) being set to "ltr".
The :-moz-only-whitespaceCSSpseudo-class matches an element that has no child nodes at all or empty text nodes or text nodes that have only white-space in them. Only when there are element nodes or text nodes with one or more characters inside the element, the element doesn't match this pseudo-class anymore.
The :-moz-system-metric(scrollbar-thumb-proportional)CSSpseudo-class will match an element if the computer's user interface uses proportional scrollbar thumbs; that is, the draggable thumb on the scrollbar resizes to indicate the relative size of the visible area of the document.