a{
    color: white;
}
header{
    height: 70px;
    line-height: 70px;
}
nav{
    background-color: #ddebf5;
}
.on{/*按钮选中样式*/
    color: black;
    border-bottom: 3px solid black;
}
body{
    font-family: 黑体;

}
footer{
    background: black;
    height: 55px;
    line-height: 55px;
    color: white;
}

li{

}