原理
使用css的定位属性position,设其值为fixed即可,该属性是将指定元素绝对定位于窗体,使用left,right,top和bottom属性来设置偏移于窗体原点的位置。
实例源码
<html>
<head>
<meta http-equiv="Content-Type" content="text/html"; charset="utf-8">
<style type="text/css">
.mainBox{
margin:0px 10px;
width:400px;
height:400px;
position:relative;
background:#FF0000;
}
.sourceBox{
float:left;
width:100px;
height:100px;
position:relative;
background:#00FFFF;
}
.fixedBox{
z-index:10;
width:100px;
height:100px;
position:fixed;
left:50px;
top:50px;
background:#00FF00;
}
</style>
</head>
<body>
<div class="fixedBox">跟随窗口
</div>
<div class="mainBox">
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
</div>
<div class="mainBox">
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
</div>
<div class="mainBox">
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
<div class="sourceBox">
</div>
</div>
</body>
</html>