<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
* {
margin: 0;
padding: 0
}
.box1 {
600px;
height: 1800px;
background-color: #ddd;
margin: 0 auto;
}
.nav {
position: fixed;
left: 0;
top: 0;
right: 0;
bottom: 0;
100%;
height: 50px;
line-height: 50px;
background: #000;
display: none;
color: #fff; font-size: 24px; text-align: center;
}
.h250 {
height: 250px;
background: #D99797
}
</style>
<script src="http://apps.bdimg.com/libs/jquery/1.9.1/jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(window).scroll(function() {
var scroHei = $(window).scrollTop();
if (scroHei > 250) {
$('.J_nav').fadeIn();
} else {
$('.J_nav').fadeOut();
}
});
</script>
</head>
<body>
<div class="box1">
<div class="nav J_nav">悬浮显示</div>
<div class="h250">高为250</div>
</div>
</body>
</html>
1.显示图：
2.滚动之后显示：
