/* 绝对居中 */
/* 方法一: */
.parent{
display: flex;
justify-content: center;
align-items: center;
}
/* 方法二 */
.parent{
100px;
height: 100px;
position: relative;
background: #ccc;
}
.child{
40px;
height: 40px;
background: #000;
position: absolute;
left:50%;
transform: translate(-50%,-50%);
}
/* 方法三 */
.parent{
100px;
height:100px;
position: relative;
background:#f91;
}
.child{
40px;
height:40px;
background:#ccc;
position: absolute;
left:0;
top:0;
bottom: 0;
right:10
}
/* 方法四 */
.parent:{
100px;
height: 100px;
display: table-cell;
background-color: #ccc;
text-align: center;
vertical-align: middle;
}
.child{
40px;
height: 40px;
background-color: #000;
display: inline-block;
}