IE6下png格式图片透明问题

.png{
 background: url(http://www.xxx.com/images/x.png) no-repeat;
 filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(enabled=true,  sizingMethod=scale, src="http://www.xxx.com/images/x.png");
 _background:none;
 width:100px;
 height:100px;
}

参考：
http://blog.gulu77.com/?p=147
http://www.cnblogs.com/yuzhongwusan/archive/2009/04/17/1438119.html
http://www.nczonline.net/blog/2007/01/03/opacity-in-ie6-alpha-or-png/
http://docs.jquery.com/Tutorials:PNG_Opacity_Fix_for_IE6