html,body,ul,li {
	margin:0;
	padding:0;
	border:0;
}
.item {
	height:500px;
	width:100%;
	background:red;
}
.aitem_list {
	display:flex;
	height:50px;
	position:fixed;
	width:100%;
	z-index:10;
	background:#ffffff;
}
.atime {
	display:flex;
	justify-content:center;
	align-items:center;
	flex:1;
}
.list {
	padding-top:50px;
}
.aitem_list .active {
	background:blue;
}
.item .item_header {
	height:50px;
	background:rebeccapurple;
	width:100%;
	display:flex;
	justify-content:center;
	align-items:center;
	color:#ffffff;
}
.item .active {
	position:fixed;
	top:50px;
}