box-sizing: content-box|border-box|inherit;
border-box可以将盒子内的border内减
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<style type="text/css">
*{
margin: 0;
padding: 0;
}
div{
width: 80%;
height: 300px;
background: pink;
margin: 50px auto;
}
p:first-child{
width: 50%;
height: 200px;
background: blue;
float: left;
border: 2px solid red;
/*指名border这个属性是这个小盒的宽度*/
box-sizing: border-box;
}
p:last-child{
width: 50%;
height: 200px;
background: green;
float: left;
border: 2px solid red;
box-sizing: border-box;
}
</style>
<body>
<div>
<p></p>
<p></p>
</div>
</body>
</html>
