Untitled

I want a image inside a list and a anchor tag to change on hover with css
<ul>
    <li><a class="nav1" href="http://localhost:8888/fiftyfity/?page_id=2"></a></li>
</ul>

ul li a.nav1{
    background-image: url("../images/nav1.gif");
    width:161px;
    height: 49px;
}
ul li a.nav1:hover{
    background-image: url("../images/navB1.gif");
    width:100px;
    height: 20px;
}

ul li a.nav1 {
 display: block;
}

ul li a.nav1{
    display:block;
    background-image: url("../images/nav1.gif");
    width:161px;
    height: 49px;
}
ul li a.nav1:hover{
    display:block;
    background-image: url("../images/navB1.gif");
    width:100px;
    height: 20px;
}