怎么输入自动换行显示？
<style type="text/css">
.mainBox{width:960px;background:#CFF;height:300px;margin:0 auto;}
.leftBox{width:100px;height:300px;background:#C9F;float:left;}
.rightBox{width:210px;height:300px;background:#FCF;float:right;}
/*在此定义相应的类选择器，并根据要求设置相关CSS属性*/
</style>
</head>
<body>
<div class="mainBox">
<div class="leftBox">leftboxssadasdshsakhahdhsakdhaskdhsadhskadhd</div>
<div class"rightBox">rightbox</div>
</div>
<!--在此添加相应的div标签-->
显示效果：在leftBox的元素都写到外面去了
