转载 http://www.cnblogs.com/jikey/archive/2012/08/31/2665880.html
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<title>Css:背景色透明，内容不透明之终极方法！兼容所有浏览器</title>
<style type="text/css">
*{margin:0;padding:0;}
body{background:#3f3f3f;font-family:"宋体", Arial;}
h1, h2, h3, h4, h5, h6{font-weight:normal;font-size:100%;}
img{border:none 0;}
#bos{820px;background:#fff;margin:0 auto;}
#bos ul{zoom:1;overflow:hidden;background:#fff;padding:5px 0 5px 5px;}
#bos ul li{260px;position:relative;overflow:hidden;float:left;margin:5px;background:#fff;}
.img_wrap{258px;border:1px solid #ccc;border-radius:15px;display:block;overflow:hidden;}
#bos ul li h2{100%;height:0px;line-height:50px;color:#fff;text-indent:1em;font-size:14px;font-family:微软雅黑;position:absolute;bottom:0px;border-bottom-left-radius:15px;border-bottom-right-radius:15px;filter:progid:DXImageTransform.Microsoft.gradient(enabled='true',startColorstr='#44000000',endColorstr='#44000000');background:rgba(0,0,0,.6);}
</style>
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<body>
<div id="bos">
<ul>
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<a class="img_wrap" href="#"><img src="http://i2.vanclimg.com/users/18/20120824/n1_120824.jpg" alt="" /></a>
<h2>网站防诈骗重要提示 购物满59元免运费</h2>
</li>
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<a class="img_wrap" href="#"><img src="http://i1.vanclimg.com/users/18/20120824/r1_120824.jpg" alt="" /></a>
<h2>Android客户端升级新体验 配送延误通知</h2>
</li>
<li>
<a class="img_wrap" href="#"><img src="http://i1.vanclimg.com/users/18/20120824/f8_120824.jpg" alt="" /></a>
<h2>陈年谈品牌的本分 工行e支付可直减60元</h2>
</li>
<li>
<a class="img_wrap" href="#"><img src="http://i2.vanclimg.com/users/18/20120824/n1_120824.jpg" alt="" /></a>
<h2>陈年谈品牌的本分 工行e支付可直减60元</h2>
</li>
<li>
<a class="img_wrap" href="#"><img src="http://i1.vanclimg.com/users/18/20120824/f8_120824.jpg" alt="" /></a>
<h2>陈年谈品牌的本分 工行e支付可直减60元</h2>
</li>
<li>
<a class="img_wrap" href="#"><img src="http://i2.vanclimg.com/users/18/20120824/n1_120824.jpg" alt="" /></a>
<h2>陈年谈品牌的本分 工行e支付可直减60元</h2>
</li>
</ul>
</div>
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var bos = document.getElementById('bos');
var lis = bos.getElementsByTagName('li');
var len = lis.length;
while (len--) {
lis[len].onmouseover = function () {
over(this.getElementsByTagName('h2')[0]);
}
lis[len].onmouseout = function () {
out(this.getElementsByTagName('h2')[0]);
}
}
function over(obj) {
var ypos = 0;
if (obj.time) {
clearInterval(obj.time)
}
obj.time = setInterval(function () {
if (ypos < 50) {
ypos += Math.ceil((50 - ypos) / 3);
}
obj.style.height = ypos + "px";
}, 25);
}
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var ypos = 50;
if (obj.time) {
clearInterval(obj.time)
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obj.time = setInterval(function () {
if (ypos >= 0) {
ypos -= Math.ceil((ypos - 0) / 3);
}
obj.style.height = ypos + "px";
}, 25);
}
// js代码解释权归华仔所有
</script></body>
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