为什么box2后面的2个<p>标签都受影响了

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
<style type="text/css">
.box1{height:50px;background:red;float:left;}
.box2{height:50px;background:blue;float:left;}
.fclear{clear:both;}/*width:100%;overflow:hidden;*/
</style>
</head>

<body>
<p>盒子1盒子1</p>
<div class="box1">盒子1盒子1</div>
<div class="box2">盒子1盒子1</div>
<p>盒子1盒子1</p>
<p>盒子1盒子1</p>

</body>
</html>