<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.wrap {
height: 30px;
overflow: hidden;
position: absolute;
top: 30;
left: 100;
width: 100%
}

p {
margin: 0;
height: 30px;
line-height: 30px;
text-align: center;
background: #ccc;
width: 300px;
}

.content p {
position: absolute;
}

@-webkit-keyframes anim1 {
0% {
top: 40px;
opacity: 1
}
50% {
top: -40px;
opacity: 1
}
75% {
top: -40px;
opacity: 0
}
100% {
top: 40px;
opacity: 0
}
}

@-webkit-keyframes anim2 {
0% {
top: -40px;
opacity: 0
}
25% {
top: 40px;
opacity: 0
}
50% {
top: 40px;
opacity: 1
}
100% {
top: -40px;
opacity: 1
}
}
.content p:nth-child(1) {
-webkit-animation: anim1 5s linear infinite;
}

.content p:nth-child(2) {
-webkit-animation: anim2 5s linear infinite;
}
</style>
</head>
<body>
<div class="wrap">
<div class="content">
<p>第一条消息</p>
<p>第二条消息</p>
</div>
</div>
</body>

</html>