source/misc/embedded_libs/fmt-8.1.1/doc/bootstrap/mixins/opacity.less
browsing at commit = 397e4b125f20ad9744f8ce5a0e617b6425a1e1cf
// Opacity
.opacity(@opacity) {
opacity: @opacity;
// IE8 filter
@opacity-ie: (@opacity * 100);
filter: ~"alpha(opacity=@{opacity-ie})";
}