为什么字母a没有自动换行,而是顶出右边了
<!DOCTYPE html>
<html>
<head>
<title></title>
<meta charset="utf-8">
<style type="text/css">
body{margin:0; padding: 0;font-size: 20px;}
div{text-align:center;line-height: 30px; }
.main{width:960px; margin:0 auto;position:relative;}
.left{background-color: red; width:200px;height:500px;position: absolute;left:0; top:0;}
.middle{height:500px;margin: 0 160px 0 200px;border:1px solid green;}
.right{background-color: blue; width:160px; height:500px;position:absolute;right:0; top:0;}
</style>
</head>
<body>
<div class="main">
<div class="left">left</div>
<div class="middle">aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa</div>
<div class="right">right</div>
</div>
</body>
</html>