source/misc/embedded_libs/fmt-8.1.1/doc/bootstrap/mixins/opacity.less
browsing at commit = b15a74147bf83ed71ab6b84313c5cb47e68d9efc
// Opacity
.opacity(@opacity) {
opacity: @opacity;
// IE8 filter
@opacity-ie: (@opacity * 100);
filter: ~"alpha(opacity=@{opacity-ie})";
}