下边是div实现两列显示没加overflow:hidden时的代码，在ie中查看效果是正常的，但在firefox中右侧的背景和边框会扩展到左侧．
<!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>firefox中div两列</title>
<style type="text/css">
.w {width:400px;}
.d1 {height:50px;float:left;}
.d2 {height:50px;background:#F9EDFA;border:2px dotted #A63DAD;}
</style>
</head>
<body>
<div class="w">
<div class="d1">左侧</div><div class="d2">右侧</div>
</div>
</body>
</html>
下边是修正后的代码，在firefox和ie中都能正常显示了
<!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>firefox中div两列</title>
<style type="text/css">
.w {width:400px;}
.d1 {height:50px;float:left;}
.d2 {height:50px;background:#F9EDFA;border:2px dotted #A63DAD;overflow:hidden}
</style>
</head>
<body>
<div class="w">
<div class="d1">左侧</div><div class="d2">右侧</div>
</div>
</body>
</html>