div块移动之后，为什么span块没有移动到现在边框的下边位置，div块不应该占据整个边框么
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>relative样式</title>
<style type="text/css">
#div1{
width:200px;
height:200px;
border:2px red solid;
position:relative;
//position:absolute;
left:100px;
top:50px;
}
</style>
</head>
<body>
