图片链接的hover事件

<style>
.a1 img {
width: 100px;
height: 31px;
background: #333 url("img/puhuo_but_2.png") no-repeat;
}

.a1:visited img {
background-image: url("img/puhuo_but_3.png");
}

.a1:hover img {
background-image: url("img/puhuo_but_1.png");
}

</style>

<div style="height:100px; wight:200; background:#ccc">
<a href="job.html" class="a1"><img src="img/puhuo_but_0.png" alt=""></a>
</div>