source/misc/embedded_libs/fmt-8.1.1/doc/bootstrap/mixins/opacity.less
browsing at commit = 7d88cb3813700a078de44f3373b18ccd8939a9fd
// Opacity
.opacity(@opacity) {
opacity: @opacity;
// IE8 filter
@opacity-ie: (@opacity * 100);
filter: ~"alpha(opacity=@{opacity-ie})";
}