if (navigator.platform == "Win32" && navigator.appName == "Microsoft Internet Explorer" && window.attachEvent) {
	window.attachEvent("onload", enableAlphaImages);
}

function enableAlphaImages()
{
	var rslt = navigator.appVersion.match(/MSIE (\d+\.\d+)/, '');
	var itsAllGood = (rslt != null && Number(rslt[1]) >= 5.5);

	if (itsAllGood) 
	{
		var obj = document.getElementById('logo');
		var bg = obj.currentStyle.backgroundImage;

		if (bg && bg.match(/\.png/i) != null) 
		{
			var img = bg.substring(5, bg.length - 2);
			var offset = obj.style["background-position"];
			obj.style.filter =
				"progid:DXImageTransform.Microsoft.AlphaImageLoader(src='" + img + "', sizingMethod='crop')";
			obj.style.backgroundImage = "url('../images/spacer.gif')";//替换透明PNG的图片
			obj.style["background-position"] = offset; // reapply
		}
	}
}