Edit in JSFiddle

    var oUl=document.getElementById('ul');
    oUl.onmouseover=function(e){
        var e=e || window.event;
        var target=e.Srcelement || e.target;
        if(target.nodeName=='LI'){
        target.style.background='#ccc';
        target.innerHTML=target.nodeName;
        }
    }


    oUl.onmouseout=function(e){
        var e=e || window.event;
        var target=e.Srcelement || e.target;
        if(target.nodeName=="LI"){
        target.style.background='';
        target.innerHTML='';
        }
    }

<ul id="ul">
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
    <li></li>
</ul>

li{
    width:280px;
    height:20px;
    font-size:16px;
    padding:2px 10px;
    line-height:20px;
    border:1px solid #999;
    margin:4px;
    list-style:none;
}