<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<style>
.div1,.div2{ width:500px; margin:20px auto}
.div1 a:hover img{filter:alpha(Opacity=80);-moz-opacity:0.8;opacity: 0.8}
.div2 a:hover img{filter:alpha(Opacity=70);-moz-opacity:0.7;opacity: 0.7}
</style>
</head>
<body>
<p>鼠标移动到图片悬停时，图片变色滤镜效果：</p>
<div class="div1"><a href="#"><img src="images/div-a-bg.png" /></a></div>
<div class="div2"><a href="#"><img src="images/an.gif" /></a></div>
</body>
</html>
原文：http://www.cnblogs.com/robt/p/4616133.html