source/misc/embedded_libs/fmt-8.1.1/doc/bootstrap/mixins/opacity.less
browsing at commit = 4ab66e1416f718d4a6d025c4d49760159d67b61d
// Opacity
.opacity(@opacity) {
opacity: @opacity;
// IE8 filter
@opacity-ie: (@opacity * 100);
filter: ~"alpha(opacity=@{opacity-ie})";
}