Cross-browser semi-transparent backgrounds using RGBA and IE filter

rgba-bg

/**
 * Cross-browser solution for semi-transparent backgrounds using RGBA.
 * Read more: http://hammerspace.co.uk/2011/10/cross-browser-alpha-transparent-background-css
 *
 * Note: in IE ARGB AA is a HEX value, not a floating point.
 * Note: there is some info that IE turns off ClearType with filters.
 *
 * 2Do: explore solution for semi-transparent foregrounds.
 * 2Do: convert to SASS mixin.
 */

.el {
	/* RGB fallback for web browsers that doesn't support RGBa, except IE<=8 */
	background:rgb(255,0,0);
	/* Reset background to transparent for IE<=8 and use `\9` IE hack to skip in other browsers */
	background: transparent\9;
	/* RGBA */
	background:rgba(255,0,0,0.3);
	/* IE <=8 ARGB gradient filter */
	filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#4cFF0000,endColorstr=#4cFF0000);
	/* Trigger hasLayout for IE */
	zoom: 1;
}

.el:nth-child(n) {
	/* Prevent IE9 which supports RGBA from stacking both RGBA value and filter */
	filter: none;
}