@mixin alpha_gradient($r, $g, $b, $hex) {
  	background: -moz-linear-gradient(left, rgba($r, $g, $b, 0) 0%, rgba($r, $g, $b, 1) 50%, rgba($r, $g, $b, 1) 100%);
	background: -webkit-gradient(linear, left top, right top, color-stop(0%, rgba($r, $g, $b, 0)), color-stop(50%, rgba($r, $g, $b, 1)), color-stop(100%, rgba($r, $g, $b, 1)));
	background: -webkit-linear-gradient(left, rgba($r, $g, $b, 0) 0%, rgba($r, $g, $b, 1) 50%, rgba($r, $g, $b, 1) 100%);
	background: -o-linear-gradient(left, rgba($r, $g, $b, 0) 0%, rgba($r, $g, $b, 1) 50%, rgba($r, $g, $b, 1) 100%);
	background: -ms-linear-gradient(left, rgba($r, $g, $b, 0) 0%, rgba($r, $g, $b, 1) 50%, rgba($r, $g, $b, 1) 100%);
	filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#00#{$hex}', endColorstr='##{$hex}', GradientType=1);
	background: linear-gradient(left, rgba($r, $g, $b, 0) 0%, rgba($r, $g, $b, 1) 50%, rgba($r, $g, $b, 1) 100%);
}