The :-moz-loading CSS pseudo-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-suppressed CSS pseudo-class matches elements representing images that were not loaded because loading images from that site has been blocked.
The :-moz-system-metric(images-in-menus) CSS pseudo-class matches an element if the computer's user interface supports images in menus.
The :-moz-system-metric(scrollbar-end-backward) CSS pseudo-class will match an element if the computer's user interface includes a backward arrow button at the end of scrollbars.
The :-moz-system-metric(scrollbar-end-forward) CSS pseudo-class will match an element if the computer's user interface includes a forward arrow button at the end of scrollbars.
The :-moz-system-metric(scrollbar-start-backward) CSS pseudo-class will match an element if the computer's user interface includes a backward arrow button at the start of scrollbars.
The :-moz-system-metric(scrollbar-start-forward) CSS pseudo-class will match an element if the computer's user interface includes a forward arrow button at the start of scrollbars.
The :-moz-system-metric(scrollbar-thumb-proportional) CSS pseudo-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.
The :-moz-system-metric(touch-enabled) CSS pseudo-class will match an element if the device on which the content is being rendered offers a supported touch-screen interface.
The :-moz-tree-cell-text(hover) CSS pseudo-class will match an element if the mouse cursor is presently hovering over text in a tree cell.
Activated when the type attribute is set to progressmeter.
The :-moz-user-disabled CSS pseudo-class matches elements representing images that were not loaded because images have been entirely disabled by the user's preferences.