<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<style>
.c1{
background-color: rgba(255,0,0,0.3);/*背景颜色或者字体颜色等单独透明度*/
height: 100px;
width: 100px;
}
.c2 {
background-color:rgb(255, 0, 0)
height: 100px;
width: 100px;
/* opacity: 0.3; 整个标签透明度 */
}
</style>
</head>
<body>
<div class="c1">你好</div>
<div class="c2">我好</div>
</body>
</html>
