<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<style>
html {
background: #f9f9f9;
overflow-y: scroll;
}
body{
font-size: 14px;
font-family: "微软雅黑";
padding: 0;
margin:0 auto;
}
#child {
position:absolute;
top:50%;
left: 50%;
100px;
height:20px;
margin:-10px 0px 0px -50px; /* negative half of the height */
background-color: #ddd;
text-align: center;
line-height:20px;
}
</style>
<body>
<div id="parent">
<div id="child">Content here</div>
</div>
</body>
</html>
<!DOCTYPE html>
<head>
<title>center</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<style>
.root {
100%;
height:100%;
display:table;
background-color: rgba(0,0,0,0.5);
position: fixed;
}
.parent {
display:table-cell;
vertical-align:middle;
}
.child {
50px;
height:50px;
background:#22B14C;
margin:0 auto;
}
</style>
</head>
<body>
<div class="root">
<div class="parent">
<div class="child"></div>
</div>
</div>
</body>
</html>
<!DOCTYPE html>
<head>
<title>center</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<style>
body{
margin:0;
padding: 0;
}
.parent {
100%;
height:100%;
border:1px solid black;
position: fixed;
background-color: rgba(0,0,0,0.5);
}
.child {
position:absolute;
50px;
height:50px;
top:50%;
left:50%;
-webkit-transform: translate(-50%,-50%);
-ms-transform: translate(-50%,-50%);
-o-transform: translate(-50%,-50%);
transform: translate(-50%,-50%);
background:#22B14C;
}
</style>
</head>
<body>
<div class="parent">
<div class="child">
</div>
</div>
</body>
</html>