.clearfix{
    &:before,&:after{
        content: "";
        display: table;
        clear: both;
    }
}
*{
    padding: 0;
    margin: 0;
}
.wrap{
    position: absolute;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    width: 600px;
    height: 600px;
    margin: auto;
    #tab{
        list-style: none;
        li{
            float: left;
            width: 150px;
            height: 50px;
            &:nth-child(1){
                background-color: #acf;
            }
            &:nth-child(2){
                background-color: #ccc;
            }
            &:nth-child(3){
                background-color: #aaa;
            }
        }
    }
    #container{
        position: relative;
        div{
            position: absolute;
            left: 0;
            top: 0;
            width: 400px;
            height: 400px;
            &:nth-child(1){
                background-color: #acf;
            }
            &:nth-child(2){
                background-color: #ccc;
            }
            &:nth-child(3){
                background-color: #aaa;
            }
        }
    }
}