LESS background alpha Mixin

bg-alpha.less

// --- Cross-browser transparent background trick thanks to
// http://hammerspace.co.uk/2011/10/cross-browser-alpha-transparent-background-css
.bg-alpha(@color, @opacity) {
	@alphaColour: hsla(hue(@color), saturation(@color), lightness(@color), @opacity);
	@ieAlphaColour: argb(@alphaColour);
	background:@color;
	background: transparent\9;
	background: rgba(red(@color), green(@color), blue(@color), @opacity);
	filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d',endColorstr='%d')", @ieAlphaColour, @ieAlphaColour));
	zoom: 1
}