png在IE6中的透明有关问题

png在IE6中的透明问题
图片是插在网页中的：        
        
          <!--[if ie 6]>
          <script>
          function correctPNG()
          {
          for(var i=0; i<document.images.length; i++)
          {
          var img = document.images[i];
          var imgName = img.src.toUpperCase();
          if (imgName.substring(imgName.length-3, imgName.length) == "PNG")
          {
          var imgID = (img.id) ? "id='" + img.id + "' " : "";
          var imgClass = (img.className) ? "class='" + img.className + "' " : "";
          var imgTitle = (img.title) ? "title='" + img.title + "' " : "title='" + img.alt + "' ";
          var imgStyle = "display:inline-block;" + img.style.cssText;
          if (img.align == "left") imgStyle = "float:left;" + imgStyle;
          if (img.align == "right") imgStyle = "float:right;" + imgStyle;
          if (img.parentElement.href) imgStyle = "cursor:hand;" + imgStyle;
          var strNewHTML = "<span "+ imgID + imgClass + imgTitle + "style=\"" + "width:" + img.width + "px; height:" + img.height + "px;" + imgStyle + ";"
          + "filter:progid:DXImageTransform.Microsoft.AlphaImageLoader" + "(src='" + img.src + "', sizingMethod='scale');\"></span>";
          img.outerHTML = strNewHTML;
          i = i-1;
          }
          }
          }
          window.attachEvent("onload", correctPNG);
          </script>
          <![endif]-->


若图片是背景：

#img a{
      background:images/text.png;
      _background:none;
      _filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(src="aimages/text.png" ,sizingMethod="crop");
       }