如下代码，三个div，我把中间的div设置为浮动，为何后面的div会和第二个重合，而文字不动
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>测试层模型的三种定位方式</title>
<style type="text/css">
#box2{
width: 50px;
height: 50px;
border: 2px solid #0000FF;
}
#box3{
width: 40px;
height: 40px;
border: 2px solid #FF0000;
}
#box4{
width: 30px;
height: 30px;
border: 2px solid #00FFFF;
}
#box3{
float:left;
}
</style>
</head>
<body>
<form action="" method="">
<div id="box2" class="box">1</div>
<div id="box3" class="box">3</div>
<div id="box4" class="box">4</div>
</form>
</body>
</html>
