The <noembed> element is a deprecated and non-standard way to provide alternative, or "fallback", content for browsers that do not support the <embed> element or do not support embedded content an author wishes to use. This element was deprecated in HTML 4.01 and above in favor of <object>. Fallback content should be inserted between the opening and closing <object> tags.
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.