使用定位和負值空白邊讓設計居中https://blog.csdn.net/InJavaWeTrust/article/details/106611395
<!DOCTYPE>
<html>
<head>
<style>
#a {
border: 1px solid red;
height: 300px;
width: 300px;
left: 50%;
position: relative;
margin-left: -150px;
}
</style>
</head>
<body>
<div id="a">
fafdafasfa dasfaf aadsfsas dasfas
</div>
</body>
</html>