求大佬解释一下，为什么超出部分不能影藏
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>背景原点</title>
<style type="text/css">
.box1 {
width:220px;
height:120px;
border:10px dashed #000;
padding:20px;
font-weight:bold;
background:#ccc url(http://static.mukewang.com/static/img/logo_index.png) no-repeat;
background-origin:content-box;
position:relative;
}
.box1 span{
position:absolute;
left:0;
top:0;
}
.box2{
border:5px solid #333;
height:44px;
text-overflow:ellipsis;
overflow:hidden;
white-space:nowrap;
}
</style>
</head>
<body>
<div class="box1"><span>padding</span>
<div class="box2">content</div>
</div>
</body>
</html>
