知识点：html标签，css样式属性，代码优化，行业规范，布局思路，javascript基础，jquery方法，逻辑思维。
html代码：

    <div class="con">
        <div class="top">
            <img src="images/my.jpg" height="667" width="500" alt="关键词" />
            <p>经典课程集</p>
        </div>
        <div class="pic-list">
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
            <div class="content">
                <div class="pic"></div>
                <div class="bq">
                    <span>2016/10/15</span>
                    <img src="images/r.png" />
                    <i></i>
                </div>
            </div>
        </div>
    </div>

css代码：

        <style>
        /*浏览器兼容问题*/
        *{margin:0;/*外边距*/padding:0;/*内边距*/}
        body{
            background:url('images/bg.jpg') fixed;
            /*background-attachment:;设置背景图是否固定或者随着页面滚动*/
        }
        .con{/*以 . 开头 class命名 类选择器*/
            width:900px;
            margin:0 auto;/*上下外边距0 左右自适应居中*/
        }
        .con .top{
            background:#fff;
            width:130px;
            height:170px;
            text-align:center;/*文本居中对齐*/
            font-size:14px;
            line-height:20px;
            margin-left:150px;
            padding-top:15px;
        }
        .con .top img{
            width:100px;
            height:auto;
            margin:0 auto;
        }
        .con .pic-list{
            width:600px;
            border-left:3px solid #00ccff;/*边框线*/
            margin-left:215px;
            padding-top:30px;
        }
        .con .pic-list .content{
            width:600px;
            height:400px;
            margin-bottom:30px;
            position:relative;/*相对定位 参照物*/
            -webkit-animation:sc 2s;/*定义动画*/
            display:none;
        }
        .con .pic-list .content .pic{
            width:590px;
            height:400px;
            margin-left:10px;
            background:rgba(0,0,0,0.5);
            border-radius:10px;/*小圆角*/
            box-shadow:0px 0px 4px 4px #737373;/*水平方向 垂直方向 虚化度 范围  颜色*/
        }
        .con .pic-list .content .bq{
            width:120px;
            height:30px;
            position:absolute;/*绝对定位*/
            top:100px;
            left:-116px;
        }
        .con .pic-list .content .bq span{
            display:block;
            background:#000;
            color:#fff;
            width:90px;
            height:30px;
            text-align:center;
            line-height:30px;
            float:left;
        }
        .con .pic-list .content .bq img{
            float:left;
            margin-top:7px;
        }
        .con .pic-list .content .bq i{
            float:right;
            width:6px;
            height:6px;
            background:#00cc33;
            border:2px solid #fff;
            border-radius:50%;
            margin-top:10px;
        }
        /*css3 动画*/
        @-webkit-keyframes sc{
            from{-webkit-transform:rotate(220deg) scale(0.2)}
            to{-webkit-transform:rotate(0deg) scale(1)}
        }
        </style>

javascript代码：

    <script src="js/jquery.js"></script>
    <script>
    //jq里面如何获取对象  $// jq函数  $('元素')
    $('.content:lt(3)').show();//找到序列号小于3的元素 显示
    //滚动事件
    $(window).scroll(function(){
        var _top = $(window).scrollTop();//获取滚动条高度
        console.log( _top );
        $('.content').each(function(){//遍历
            var _index = $(this).index()+1;//当前序列号
            var _height = $(this).offset().top;//获取到当前content到浏览器窗口顶部距离
            if( _top < _height ){//优先原则
                $('.content:lt('+_index+')').show();
                $('.content:gt('+_index+')').hide();
                return false;//t跳出遍历
            }
        });
    });
    </script>