多种方式垂直水平居中

 <div class="wrapper">
        <div class="content"></div>
    </div>

.wrapper {
    display: table-cell;
    width: 500px;
    height: 500px;
    text-align: center; /*水平居中*/
    border: 1px solid #eee;
    vertical-align: middle; /*图片垂直居中*/
    position: relative;
    
} 
.content {
    width: 200px;
    height: 200px;
    background-color: red;
    margin: auto;
}

<div class="wrapper">
        <div class="content"></div>
    </div>

.wrapper {
    display: table-cell;
    width: 500px;
    height: 500px;
    text-align: center; /*水平居中*/
    border: 1px solid #eee;
    vertical-align: middle; /*图片垂直居中*/
    position: relative;
    
} 
.content {
    width: 200px;
    height: 200px;
    background-color: red;
    position: absolute;
    left: 50%;
    right: 50%;
   transform: translate(-50%, -50%);
}

<div class="wrapper">
        <div class="content"></div>
    </div>

.wrapper {
    width: 500px;
    height: 500px;
    border: 1px solid #eee;
    display:flex;
    justify-content:center;
    align-items: center;  
} 
.content {
    width: 200px;
    height: 200px;
    background-color: red;
}

<div class="wrapper">
        <div class="content"></div>
    </div>

.wrapper {
    width: 500px;
    height: 500px;
    border: 1px solid #eee;
    position: relative;
} 
.content {
    width: 200px;
    height: 200px;
    background-color: red;
    position: absolute;
    left: 50%;
    top: 50%;
    /*自身宽高一半的负值*/
    margin-left: -100px;
    margin-top: -100px;
}