JS代码：

function correctPNG(){
   for(var i=0; i<document.images.length; i++)
      {
     var img = document.images
     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:pointer;" + 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);

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

function alphaBackgrounds(){
   var rslt = navigator.appVersion.match(/MSIE (d+.d+)/, '');
   var itsAllGood = (rslt != null && Number(rslt[1]) >= 5.5);
   for (i=0; i<document.all.length; i++){
      var bg = document.all.currentStyle.backgroundImage;
      if (itsAllGood && bg){
         if (bg.match(/.png/i) != null){
            var mypng = bg.substring(5,bg.length-2);
            document.all.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='"+mypng+"', sizingMethod='scale')";
            document.all.style.backgroundImage = "url('')";
         }
      }
   }
}

alphaBackgrounds();

代码下载：PNGTrans.rar

链接JS代码：

<script type="text/javascript" src="Pic/PNGTrans.js"></script>