.parent {
position: relative;
}
.child {
position: absolute;
left: 50%;
top: 50%;
transform: translate(-50%, -50%);
}.parent {
display: flex;
justify-content: center;
align-items: center;
}center{
display: block;
margin-left: auto;
margin-right: auto;
width: 50%;
}.class {
text-align: center;
}/*ADD MARGIN auto to left and right*/
.box1{
width:80%;
margin:0 auto;
}//Center DIV HTML5
<body>
<div style="width:800px; margin:0 auto;">
centered content
</div>
</body>