<style type="text/css">
 *{padding:0;margin:0;}
 a{text-decoration:none;}
 html,body{height:100%;width:100%;background:black;}
 ul{position:relative;width:990px;list-style:none;background:white;display: flex;flex-direction:row;justify-content: space-around;margin:50px auto;border-radius:10px;}
 ul li{position: relative;flex:1;text-align:center;}
 ul li a{font-size:18px;color:#333;padding:10px 0;display: block;}
 .cloud{position:absolute;left:32px;top:0;bottom:0;margin:auto;width:83px;height:42px;background:url('images/cloud.gif');}
 </style>

<ul>
 <span class="cloud"></span>
 <li> <a href="javascript:viod(0)" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >首頁 </a></li>
 <li><a href="javascript:viod(0)" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >電視劇</a></li>
 <li><a href="javascript:viod(0)" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >最新電影</a></li>
 <li><a href="javascript:viod(0)" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >新聞?lì)^條</a></li>
 <li><a href="javascript:viod(0)" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >八卦娛樂</a></li>
 <li><a href="javascript:viod(0)" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >軍事熱點(diǎn)</a></li>
 </ul>

 <script type="text/javascript">
 //獲得類為cloud的標(biāo)簽，
 var pic=document.getElementsByClassName('cloud')[0];
 //獲得所有的 li 標(biāo)簽
 var liList=document.getElementsByTagName('li');
 //定義向右的移動(dòng)初始距離
 var liLeft=32;
 //定義緩慢動(dòng)畫的初始值
 var header=32;
 //用于定義當(dāng)鼠標(biāo)點(diǎn)擊時(shí)的初始位置
 var currentLeft=32;
 for(var i=0;i<liList.length;i++){
 //鼠標(biāo)放上事件
 liList[i].onmouseover=function(){
 //獲取目標(biāo)距離
 liLeft = this.offsetLeft+this.offsetWidth/2-pic.offsetWidth/2;
 }
 //鼠標(biāo)移除事件
 liList[i].onmouseout=function(){
 //當(dāng)鼠標(biāo)移除某個(gè)li的時(shí)候把目標(biāo)距離改為初始狀態(tài)
 liLeft=currentLeft;
 }
 //鼠標(biāo)點(diǎn)擊事件
 liList[i].onclick=function(){
 currentLeft=this.offsetLeft+this.offsetWidth/2-pic.offsetWidth/2;
 }
 
 }
 //定義緩慢動(dòng)畫
 setInterval(function(){
 header = header + (liLeft-header)/10;
 pic.style.left = header + 'px';
 },20);
 </script>