方法有很多這裡列出幾種常用的
CSS代碼如下 父元素類名以out打頭，子元素類名以in打頭 one,two…代表不同的方法
<style>
*{
padding: 0;
margin: 0;
}
[class*=out]{
width: 200px;
height: 200px;
background-color: pink;
margin: 20px;
}
[class*=in]{
width: 100px;
height: 100px;
background-color: black;
}
.out-one{
display: table-cell;
vertical-align: middle;
text-align: center;
}
.in-one{
display: inline-block;
vertical-align: middle;
}
.out-two{
position: relative;
}
.in-two{
position: absolute;
margin: auto;
left: 0;
right: 0;
top: 0;
bottom: 0;
}
.out-three{
position: relative;
}
.in-three{
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%,-50%);
}
.out-four{
display: flex;
align-items: center;
justify-content: center;
}
.in-four{
}
.out-five{
display: flex;
}
.in-five{
margin: auto;
}
.out-six{
position: relative;
}
.in-six{
position: absolute;
left: 50%;
top: 50%;
margin-left: -50px;
margin-top: -50px;
}
</style>
HTML代碼
<body>
<!-- display:table-cell -->
<div class="out-one">
<div class="in-one"></div>
</div>
<!-- position + margin -->
<div class="out-two">
<div class="in-two"></div>
</div>
<!-- position + transform -->
<div class="out-three">
<div class="in-three"></div>
</div>
<!-- display:flex align-items: center;justify-content: center -->
<div class="out-four">
<div class="in-four"></div>
</div>
<!-- display:flex margin:auto -->
<div class="out-five">
<div class="in-five"></div>
</div>
<!-- position -->
<div class="out-six">
<div class="in-six"></div>
</div>
</body>
![CSS的僞元素和僞類的差別[圖]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)