当鼠标浮上时弹出一个覆盖层

<div class="content">
<ul>
<li>
<a href=""><img src="images/login-logo.png" alt="" /></a>
<div>
<p>123</p>
<p>大家好</p>
<p>怎么实现的</p>
</div>
</li>
<li>
<a href=""><img src="images/login-logo.png" alt="" /></a>
<div></div>
</li>
<li>
<a href=""><img src="images/login-logo.png" alt="" /></a>
<div></div>
</li>
</ul>
</div>
</div>

<script type="text/javascript" src="js/jquery-1.10.2.min.js"></script>
<script type="text/javascript">
$(document).ready(function(e) {
$(".content ul li a").mouseenter(function(){
$this=$(this);
$this.siblings().animate({top:"60px"});    
}).mouseleave(function(){
$this=$(this);
$this.siblings().animate({top:"124px"});    
});
});
</script>

<style type="text/css">
.content ul{overflow:hidden;}
.content ul li{list-style:none;width:124px;height:126px;overflow:hidden;margin-bottom:20px;position:relative;}
.content ul li div{width:124px;height:65px;top:124px;position:absolute;z-index:100;background-color:#000;opacity:0.3;filter:alpha(opacity=40)/*ie8--*/;progid:DXImageransform.Microsoft.Alpha(opacity=40)/*ie8*/}

</style>

或者直接用样式，但是不支持ie8-

.content ul li:hover div{top:60px;transition:top 0.2s ease-in;}