.center {
 width: 1100px;
 min-height: 600px;
 margin-left: auto;
 margin-right: auto;
}

.center_top {
 height: 40px;
 width: 1100px;
 line-height: 40px;
 border: 1px solid white;
}

.center_bottom {
 width: 900px;
 min-height: 560px;
 margin-left: auto;
 margin-right: auto;
 border-left: 1px solid white;
 border-right: 1px solid white;
 border-bottom: 1px solid white;
}