.warp{
    width: 100%;
    max-width: 1920px;
    height: auto;
    margin: 0 auto;
}
.hd-top{
    width: 1200px;
    height: 76px;
    margin: 0 auto;
    background: #ffffff;
}
.hd-nav-bg{
    width: 100%;
    height: 340px;
    overflow: hidden;
    background: url(nav_bg.jpg) no-repeat center center;
}