信息排列效果

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>无标题文档</title>

    <style type="text/css">
        *{margin:0px;padding:0px;}
        body{font-size:14px;}
        a{text-decoration:none;}
        ul,li{list-style:none;}
        #box{height:auto;550px;border:1px solid #aaa;margin:0 auto;overflow:hidden;}
        .top{height:40px;}
        .top a{height:16px; 16px;display:block;float:right;margin:5px;}
        .btn-list-off{background:#fff url(btns.jpg) no-repeat -38px 0px;}
        .btn-car-on{background:#fff url(btns.jpg) no-repeat -21px -34px;}
        .btn-list-on{background:#fff url(btns.jpg) no-repeat -21px 0px;}
        .btn-car-off{background:#fff url(btns.jpg) no-repeat -38px -32px;}

        #box ul li{height:auto;164px;border:1px solid #aaa;
                    float:left;margin:7px;
        }
        .a-img{
            height:164px;164px;display:block;overflow:hidden;
        }
        p a,p span{
            display:block;
            line-height:23px;
            padding-left:10px;
        }
        .bottom{height:40px;line-height:40px;text-align:center;background-color:#ccc;}
        .small{height:50px;50px;float:left;margin:5px;}
    </style>
    <script type="text/javascript">
        window.onload =function(){   //@@问题：window.onload 的作用是什么？
            //获取按钮
            var listBtn = document.getElementById("btn1");
            var carBtn = document.getElementById("btn2");
            var imgs = document.getElementsByTagName("img");//@@问题：如何获取多个DOM元素？

            listBtn.onclick = function(){
                //改变按钮的class的值                     //@@问题:如何改变一个元素的样式？
                listBtn.className  = "btn-list-on";
                carBtn.className = "btn-car-off";
                //改变每一个图片的路径以及它的对应的父节点的class的值
                for(var i=0;i<imgs.length;i++)
                {
                    imgs[i].src = "small.jpg";                //@@问题，怎么更换一个图片呢？
                    imgs[i].parentNode.className = "a-img small"; //@@问题，怎么获取一个元素的父节点？
                }
            }
            carBtn.onclick = function(){
                //改变按钮的class
                listBtn.className  = "btn-list-off";
                carBtn.className = "btn-car-on";
                //改变每一个图片的路径以及它的对应的父节点的class的值
                for(var i=0;i<imgs.length;i++)
                {
                    imgs[i].src = "big.jpg";
                    imgs[i].parentNode.className = "a-img";
                }
            }



        }

    </script>
</head>

<body>

<div id="box">
    <div class="top">
        <a href="#" title="列表模式" id="btn1" class="btn-list-off"></a>
        <a href="#" title="卡片模式" id="btn2" class="btn-car-on"></a>
    </div>
    <ul>
        <li>
            <div class="con">
                <a href="#" class="a-img ">
                    <img src="big.jpg" />
                </a>
                <p>
                    <a href="#">科比</a>
                    <span>洛杉矶</span>
                    <span>21个共同好友</span>
                </p>
            </div>
            <div class="bottom">
                未分组的好友
            </div>
        </li>

        <li>
            <div class="con">
                <a href="#" class="a-img">
                    <img src="big.jpg"/>
                </a>
                <p>
                    <a href="#">科比</a>
                    <span>洛杉矶</span>
                    <span>21个共同好友</span>
                </p>
            </div>
            <div class="bottom">
                未分组的好友
            </div>
        </li><li>
        <div class="con">
            <a href="#" class="a-img">
                <img src="big.jpg"/>
            </a>
            <p>
                <a href="#">科比</a>
                <span>洛杉矶</span>
                <span>21个共同好友</span>
            </p>
        </div>
        <div class="bottom">
            未分组的好友
        </div>
    </li>
        <li>
            <div class="con">
                <a href="#" class="a-img">
                    <img src="big.jpg"/>
                </a>
                <p>
                    <a href="#">科比</a>
                    <span>洛杉矶</span>
                    <span>21个共同好友</span>
                </p>
            </div>
            <div class="bottom">
                未分组的好友
            </div>
        </li><li>
        <div class="con">
            <a href="#" class="a-img">
                <img src="big.jpg"/>
            </a>
            <p>
                <a href="#">科比</a>
                <span>洛杉矶</span>
                <span>21个共同好友</span>
            </p>
        </div>
        <div class="bottom">
            未分组的好友
        </div>
    </li><li>
        <div class="con">
            <a href="#" class="a-img">
                <img src="big.jpg"/>
            </a>
            <p>
                <a href="#">科比</a>
                <span>洛杉矶</span>
                <span>21个共同好友</span>
            </p>
        </div>
        <div class="bottom">
            未分组的好友
        </div>
    </li>
    </ul>
</div>
</body>
</html>
效果：
图片
2017-09-05 23:12:45