bootstrap mouse hover
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<style>
.cls_effect{
background-color:#0084ff;
color:#FFFFFF;
padding:10px;
border:2px solid;
border-radius:5px;
text-align:center;
}
.cls_effect:hover{
opacity: 0.5;
}
</style>
</head>
<body>
<div class="container">
<h1>Hello World!</h1>
<p>opacity: 0.5; /*透明度設為 0.5*/</p>
<br>
<div class="row">
<div class="col-xs-3 col-sm-3 ">
<div class="cls_effect">
1234
</div>
</div>
<div class="col-xs-3 col-sm-3 ">
<div class="cls_effect">
567
</div>
</div>
<div class="col-xs-3 col-sm-3 ">
<div class="cls_effect">
89
</div>
</div>
<div class="col-xs-3 col-sm-3 ">
<div class="cls_effect">
1
</div>
</div>
</div>
</div>
</body>
</html>
範例 :