网上有很多是将PNG图片做为对象背景实现透明，如果需要实现<img>标签的透明，可以在PNG图片代码后面插入以下Javascript代码，可以实现页面所有PNG图透明度。

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<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>