michael@0: input, textarea, select, button,
michael@0: *:optional {
michael@0:   visibility: hidden;
michael@0: }
michael@0: 
michael@0: *:required {
michael@0:   visibility: visible;
michael@0: }
michael@0: 
michael@0: /* Override the default style. */
michael@0: :invalid {
michael@0:   box-shadow: none;
michael@0: }