我的字体怎么没反应

[data-icon]:after{
    content:attr(data-icon);
    width:260px;
    height:260px;
    background-color:#ddd;
    color:#fff;
    font-size:90px;
    text-align:center;
    line-height:260px;
    position:absolute;
    left:50%;
    top:50%;
}