.clearfix::before,
.clearfix::after{
    content:'';
    display:table;
    clear:both;
}

.w{
    width: 990px;
    margin: 0 auto;
}

body{
        user-select: none;
        font: 14px/1.5 Helvetica Neue,Helvetica,Arial,Microsoft Yahei,Hiragino Sans GB,Heiti SC,WenQuanYi Micro Hei,sans-serif;
        color: #333;
    }

a{
    text-decoration: none; 
}