我把box2和box3浮动,也就是脱离表转文档流了,后面的box4没设浮动,box4为什么没有上移,占掉box2,3的空间呢?
<!doctype html>
<html>
<head>
<meta charset="utf-8"/>
<title></title>
<style>
.box1{
width:700px;
height:700px;
background-color:#0554B8;
}
.box2{
width:350px;
height:350px;
background-color:#B9998B;
float:left;
}
.box3{
width:350px;
height:350px;
background-color:#DC5825;
}
.box4{
width:700px;
height:350px;
background-color:#050505;
}
</style>
</head>
<body>
<div class="box1">
<div class="box2">
</div>
<div class="box3">
</div>
<div class="box4">
</div>
</div>
</body>
</html>
