这个效果用js怎么做呢？

<title>51du.cn-代码演示专用页面</title> <style type="text/css"> /* 全局CSS定义 */ body { text-align: center; margin:0; padding:0; background: #FFF; font-size:12px; color:#000;} div,form,img,ul,ol,li,dl,dt,dd {margin: 0; padding: 0; border: 0;} h1,h2,h3,h4,h5,h6 { margin:0; padding:0;} table,td,tr,th{font-size:12px;} /* 链接颜色 */ a:link {color: #000; text-decoration:none;} a:visited {color: #83006f;text-decoration:none;} a:hover {color: #c00; text-decoration:underline;} a:active {color: #000;} /* 颜色属性 [定义规则，小写c加颜色名称] */ .cRed,a.cRed:link,a.cRed:visited{ color:Red; } .cBlue,a.cBlue:link,a.cBlue:visited{color:#1f3a87;} a.cBlue:hover{color:#bc2931;} .cDRed,a.cDRed:link,a.cDRed:visited{ color:#c00;} .cGray,a.cGray:link,a.cGray:visited{ color: #4F544D;} .cDGray,a.cDGray:link,a.cDGray:visited{ color: #666;} .cWhite,a.cWhite:link,a.cWhite:visited{ color:#fff;} .cBlack,a.cBlack:link,a.cBlack:visited{color:#000;} a.cBlack:hover{color:#bc2931;} /* 头图 */ .col{margin: 20 0 0 0;float:center; width:252px;border:1px solid #006BB6;} .focusPic{margin:0 auto; width:252px;} .focusPic .pic{margin:0 auto; width:250px; height:191px; padding:5px 0 0; background:url(http://cimg2.163.com/ent/newimg/focus3_bg.gif) no-repeat;} .focusPic .pic img{margin:6px 0 0 0;} .focusPic .pic h3 {text-align:left; padding:1px 0 0 12px;} .focusPic .pic h3 img {margin:0px; } .focusPic .pic .flashBlank {margin:0 auto; width:100%; height:6px; font-size:1px; } .focusPic .pic h5 {text-align:left; padding:0px 0 0 12px !important;padding:5px 0 0 12px;} .focusPic .pic h5 img {margin:0px; } .focusPic h2{ float:left; width:236px;padding:4px 0 3px 12px; font-size:14px; text-align:left;} .focusPic p{float:left; width:236px;line-height:160%; margin:0; text-align:left;padding:0 0 10px 12px; height:57px;} .focusPic .more{ margin:0 auto; width:250px; } .focusPic .more .textNum{float:right; margin:0 8px 0 0;padding:0 0 4px;} .focusPic .more .textNum .text{float:left; font-weight:bold; padding:7px 6px 0 0; color:#666;} .focusPic .more .textNum .num{float:left; width:113px; height:19px;} .focusPic .more .textNum .bg1{ background:url(http://ent.163.com/newimg/num1.gif);} .focusPic .more .textNum .bg2{ background:url(http://ent.163.com/newimg/num2.gif);} .focusPic .more .textNum .bg3{ background:url(http://ent.163.com/newimg/num3.gif);} .focusPic .more .textNum .bg4{ background:url(http://ent.163.com/newimg/num4.gif);} .focusPic .more .textNum .num ul{ float:left; width:113px;} .focusPic .more .textNum .num li{float:left; width:28px; font-weight:bold;display:block; color:#fff; list-style-type:none; padding:6px 0 0;} .focusPic .more .textNum .num li a{color:#fff; padding:0 5px; } .focusPic .more .textNum .num li a:visited{color:#fff;} .focusPic .more .textNum .num li a:hover{color:#ff0;} </style> <div class="col"> <!-- 头图 --> <script language="javascript"> var nn; nn=1; setTimeout('change_img()',6000); function change_img() { if(nn>4) nn=1 setTimeout('setFocus1('+nn+')',6000); nn++; tt=setTimeout('change_img()',6000); } function setFocus1(i) { selectLayer1(i); } function selectLayer1(i) { switch(i) { case 1: document.getElementById("focusPic1").style.display="block"; document.getElementById("focusPic2").style.display="none"; document.getElementById("focusPic3").style.display="none"; document.getElementById("focusPic4").style.display="none"; document.getElementById("focusPic1nav").style.display="block"; document.getElementById("focusPic2nav").style.display="none"; document.getElementById("focusPic3nav").style.display="none"; document.getElementById("focusPic4nav").style.display="none"; break; case 2: document.getElementById("focusPic1").style.display="none"; document.getElementById("focusPic2").style.display="block"; document.getElementById("focusPic3").style.display="none"; document.getElementById("focusPic4").style.display="none"; document.getElementById("focusPic1nav").style.display="none"; document.getElementById("focusPic2nav").style.display="block"; document.getElementById("focusPic3nav").style.display="none"; document.getElementById("focusPic4nav").style.display="none"; break; case 3: document.getElementById("focusPic1").style.display="none"; document.getElementById("focusPic2").style.display="none"; document.getElementById("focusPic3").style.display="block"; document.getElementById("focusPic4").style.display="none"; document.getElementById("focusPic1nav").style.display="none"; document.getElementById("focusPic2nav").style.display="none"; document.getElementById("focusPic3nav").style.display="block"; document.getElementById("focusPic4nav").style.display="none"; break; case 4: document.getElementById("focusPic1").style.display="none"; document.getElementById("focusPic2").style.display="none"; document.getElementById("focusPic3").style.display="none"; document.getElementById("focusPic4").style.display="block"; document.getElementById("focusPic1nav").style.display="none"; document.getElementById("focusPic2nav").style.display="none"; document.getElementById("focusPic3nav").style.display="none"; document.getElementById("focusPic4nav").style.display="block"; break; } } </script> <div class="focusPic"> <div id="focusPic1" style="display: block;"> <div class="pic"> <a href="http://ent.163.com/06/0410/07/2EB5MT7000031H2L.html"><img src="http://cimg2.163.com/ent/2006/4/10/200604100850175803c.jpg" alt="章子怡黑衣蒙头上吴彦祖保姆车" width="228" height="150" border="0" /></a> <h3><a href="http://adclient.163.com/event.ng/Type=click&FlightID=54129&AdID=56109&TargetID=515&Values=31 ,43,51,60,72,78,85,91,100,110,312,330,332,364,594,702,733,734&Redirect=http://www.eiser.net/j_163_enter_spo1.htm"><img src="http://cimg2.163.com/ent/newimg/focus2_sony.gif" width="104" height="21" alt="" /></a></h3> </div> <h2><a href="http://ent.163.com/06/0410/07/2EB5MT7000031H2L.html">章子怡黑衣蒙头上吴彦祖保姆车</a></h2> <p>　　章子怡日前和霍启山闹分手，前晚(4月8日)在香港又被媒体跟拍到她和吴彦祖一起玩乐、还一上车就遮遮掩掩 <img src="http://cimg2.163.com/ent/newimg/i4.gif" alt="详细" width="3" height="13" /> <a href="http://ent.163.com/06/0410/07/2EB5MT7000031H2L.html" class="cDRed">详细</a></p> </div> <div id="focusPic2" style="display: none;"> <div class="pic"> <a href="http://ent.163.com/06/0410/13/2EBQ6RK000031NKO.html"><img src="http://cimg2.163.com/ent/2006/4/10/2006041016571088ffc.jpg" alt="刘晓庆重演武则天造型曝光" width="228" height="150" border="0" /></a> <h3><a href="http://adclient.163.com/event.ng/Type=click&FlightID=54129&AdID=56109&TargetID=515&Values=31 ,43,51,60,72,78,85,91,100,110,312,330,332,364,594,702,733,734&Redirect=http://www.eiser.net/j_163_enter_spo1.htm"><img src="http://cimg2.163.com/ent/newimg/focus2_sony.gif" width="104" height="21" alt="" /></a></h3> </div> <h2><a href="http://ent.163.com/06/0410/13/2EBQ6RK000031NKO.html">刘晓庆重演武则天造型曝光</a></h2> <p>　　《日月凌空》正紧张拍摄,刘晓庆再次扮演武则天,记者通过特殊渠道获得了两张被称为剧组顶级机密的造型照。 <img src="http://cimg2.163.com/ent/newimg/i4.gif" alt="详细" width="3" height="13" /> <a href="http://ent.163.com/06/0410/13/2EBQ6RK000031NKO.html" class="cDRed">详细</a></p> </div> <div id="focusPic3" style="display: none;"> <div class="pic"> <a href="http://adclient.163.com/event.ng/Type=click&FlightID=55136&AdID=57068&TargetID=515&Values=31,43,51,60,72,78,81,90,100,110,312,330,332,364,582,733,734&Redirect=http://ent.163.com/special/00031SST/FQ.html"><img src="http://cimg2.163.com/ent/2006/4/7/20060407101802517a6.jpg" alt="赢飞利浦768手机" width="228" height="150" border="0" /></a> <h3><a href="http://adclient.163.com/event.ng/Type=click&FlightID=54129&AdID=56109&TargetID=515&Values=31 ,43,51,60,72,78,85,91,100,110,312,330,332,364,594,702,733,734&Redirect=http://www.eiser.net/j_163_enter_spo1.htm"><img src="http://cimg2.163.com/ent/newimg/focus2_sony.gif" width="104" height="21" alt="" /></a></h3> </div> <h2><a href="http://adclient.163.com/event.ng/Type=click&FlightID=55136&AdID=57068&TargetID=515&Values=31,43,51,60,72,78,81,90,100,110,312,330,332,364,582,733,734&Redirect=http://ent.163.com/special/00031SST/FQ.html">赢飞利浦768手机</a></h2> <p>　　参加飞利浦手机娱乐关键字专题活动，赢取飞利浦768手机，活动正火热进行中 <img src="http://cimg2.163.com/ent/newimg/i4.gif" alt="详细" width="3" height="13" /> <a href="http://adclient.163.com/event.ng/Type=click&FlightID=55136&AdID=57068&TargetID=515&Values=31,43,51,60,72,78,81,90,100,110,312,330,332,364,582,733,734&Redirect=http://ent.163.com/special/00031SST/FQ.html" class="cDRed">详细</a></p> </div> <div id="focusPic4" style="display: none;"> <div class="pic"><div class="clear flashBlank">　</div> <object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,29,0" width="228" height="150"> <param name="movie" value="http://cimg3.163.com/ent/2006/0403/pepsi228150.swf" /> <param name="quality" value="high" /> <embed src="http://cimg3.163.com/ent/2006/0403/pepsi228150.swf" quality="high" pluginspage="http://www.macromedia.com/go/getflashplayer" type="application/x-shockwave-flash" width="228" height="150"></embed> </object> <h5><a href="http://adclient.163.com/event.ng/Type=click&FlightID=54129&AdID=56109&TargetID=515&Values=31 ,43,51,60,72,78,85,91,100,110,312,330,332,364,594,702,733,734&Redirect=http://http://www.eiser.net/j_163_enter_spo1.htm"><img src="http://cimg2.163.com/ent/newimg/focus2_sony.gif" width="104" height="21" alt="" /></a></h5> </div> <h2><a href="http://adclient.163.com/event.ng/Type=click&FlightID=54561&AdID=56510&TargetID=515&Values=31,43,51,60,72,78,84,91,100,110,312,330,332,364,586,702,733,734&Redirect=http://pepsi.163.com/">中国无名小子挑战球星贝克汉姆</a></h2> <p>　　两个中国无名小子将会亲身与贝克汉姆、罗纳尔迪尼奥、亨利等世界顶级球星面对面。 <img src="http://cimg2.163.com/ent/newimg/i4.gif" alt="详细" width="3" height="13" /> <a href="http://adclient.163.com/event.ng/Type=click&FlightID=54561&AdID=56510&TargetID=515&Values=31,43,51,60,72,78,84,91,100,110,312,330,332,364,586,702,733,734&Redirect=http://pepsi.163.com/" class="cDRed">详细</a></p> </div> <div class="more"> <div class="textNum"> <div class="text">&gt; 更多头图新闻</div> <div class="num bg1" id="focusPic1nav" style="display: block;"> <ul> <li>1</li><li><a href="javascript:setFocus1(2);" target="_self">2</a></li><li><a href="javascript:setFocus1(3);" target="_self">3</a></li><li><a href="javascript:setFocus1(4);" target="_self">4</a></li> </ul> </div> <div class="num bg2" id="focusPic2nav" style="display: none;"> <ul> <li><a href="javascript:setFocus1(1);" target="_self">1</a></li><li>2</li><li><a href="javascript:setFocus1(3);" target="_self">3</a></li><li><a href="javascript:setFocus1(4);" target="_self">4</a></li> </ul> </div> <div class="num bg3" id="focusPic3nav" style="display: none;"> <ul> <li><a href="javascript:setFocus1(1);" target="_self">1</a></li><li><a href="javascript:setFocus1(2);" target="_self">2</a></li><li>3</li><li><a href="javascript:setFocus1(4);" target="_self">4</a></li> </ul> </div> <div class="num bg4" id="focusPic4nav" style="display: none;"> <ul> <li><a href="javascript:setFocus1(1);" target="_self">1</a></li><li><a href="javascript:setFocus1(2);" target="_self">2</a></li><li><a href="javascript:setFocus1(3);" target="_self">3</a></li><li>4</li> </ul> </div> </div> </div> </div>
 提示：您可以先修改部分代码再运行