请问实现效果是否正确？

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
    <style type="text/css">
        *{
            padding:0;
            margin:0;
        }
        body,html{
            width:100%;
            height:100%;
        }
        .con{
            width:100%;
            height:4033px;
            background:url("http://img1.sycdn.imooc.com/climg//59c9f7ce0001839219034033.png") center top no-repeat;
        }
        .left-nav{
            left: 0;
            background:url("http://img1.sycdn.imooc.com/climg//5a3383d00001a3dd02240364.png") no-repeat;
        }
        .right-nav{
            right: 0;
            background: url("http://img1.sycdn.imooc.com/climg//5a3383c70001f1b702240364.png") no-repeat;
        }
        .right-nav,.left-nav{
            top: 50%;
            margin-top: -289px;
            width: 460px;
            height: 578px;
            position: fixed;
        }
    </style>
</head>
<body>
<div class="con">
    <div class="left-nav"></div>
    <div class="right-nav"></div>
</div>
</body>
</html>

我想问下为什么我的效果是这样的，有哪里不正确吗？