#top{
    background-image: url("beijing1.jpg");
    background-size: 100% 100%;
}
#dibu{
    background-image: url("beijing2.jpg");
    background-size: 100% 100%;
}


#dibu div{

    text-align: center;
    float: left;
    width: 50%;
    height: 100%;
}

footer{
    background: #999999;
}