请问怎么让它们另起一行显示？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>怎么整？</title>
<style type="text/css">
#div1,#div2{
width: 300px;
height: 300px;
border:1px blue solid;
float: left;
}
#div3,#div4{
width: 300px;
height: 300px;
border:1px pink solid;
float: right;
}
#div5,#div6{
width: 300px;
height: 300px;
border:1px red solid;
}
#div5{float: left;}
#div6{float: right;}
</style>
</head>
<body>
<div id="div1">栏目one</div>
<div id="div2">栏目two</div>
<div id="div3">栏目three</div>
<div id="div4">栏目four</div>
<div id="div5">栏目five</div>
<div id="div6">栏目six</div>
</body>
</html>全都挤在一起了，不知道咋整才可以，求解？
