[SCSS] Cross Browser alpha background colour mixin

_rgba-background.scss

@mixin rgba-background($color, $opacity) {
	$rgba: rgba($color, $opacity);
	$IEcolor: ie_hex_str($rgba);
	filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#{$IEcolor}', endColorstr='#{$IEcolor}', GradientType=0 );
	background: $rgba;
}

usage:

.div {
    @include rgba-background(#f0f, 0.7);
}