<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Gradient</title>
<style type="text/css">
p {
width: 400px;
height: 150px;
line-height: 150px;
text-align:center;
color: #000;
font-size:24px;
background-image:linear-gradient(to top left,#fff,#999,red,green,blue,pink);
border: 20px solid pink;
box-shadow:20px,20px,20px,red;
}
</style>
</head>
<body>
<p>右下角向左上角的线性渐变背景</p>
</body>
</html>
box-shadow中用空格隔开不要用逗号
你把 box-shadow:20px,20px,20px,red;改成box-shadow:20px 20px 20px red;就行了。