老师请问我这样设置是对的吗？

 .content{
            width:800px;
            height:400px;
            background-color: skyblue;
            position:relative;
        }
 .top{
            width:400px;
            height:200px;
            background-color: yellow;
            position:absolute;
            box-sizing: content-box;
            margin-top:100px;
            margin-right:200px;
            margin-bottom:100px;
            margin-left:200px; 
        }