父元素text-align:center;子元素：inline-block;
优点：兼容性好；
不足：需要同时设置子元素和父元素
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>水平居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
text-align: center;
}
.child {
display: inline-block;
width: 300px;
height: 100px;
background: blue;
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html>子元素margin:0 auto;
优点：兼容性好
缺点：需要指定宽度
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>水平居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
}
.child {
width: 300px;
height: 100px;
background: blue;
margin:0 auto;
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html>子元素{display:table;margin:0 auto;}
优点:只需要对自身进行设置
不足:IE6,7需要调整结构
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>水平居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
}
.child {
width: 300px;
height: 100px;
background: blue;
margin:0 auto;
display:table;margin:0 auto;s
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html>父元素：relative；子元素：absolute；left:50%;margin-left:-宽度的一半
优点：兼容性好
缺点：需要知道子元素的宽度
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>水平居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
position: relative;
top: 0;
left: 0;
}
.child {
width: 300px;
height: 100px;
background: blue;
position: absolute;
top: 0;
left: 50%;
margin-left: -150px;
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html>父元素：relative；子元素：absolute；left:50%;transform:translate(-50%,0);
优点：兼容性差
缺点：不需要知道子元素的宽度
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>水平居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
position: relative;
top: 0;
left: 0;
}
.child {
width: 300px;
height: 100px;
background: blue;
position: absolute;
top: 0;
left: 50%;
transform: translate(-50%,0);
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html>弹性盒子：父元素：display:flex;justify-content:center;
优点：简单
缺点：兼容性差
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>水平居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
display: flex;
justify-content: center;
}
.child {
width: 300px;
height: 100px;
background: blue;
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html>vertical-align:center;
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>水平居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
display:table-cell;
vertical-align:middle;
}
.child {
width: 300px;
height: 100px;
background: blue;
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html><!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>垂直居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
vertical-align:middle;
line-height:450px;
}
.child {
width: 300px;
height: 100px;
background: blue;
display:inline-block;
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html>
<!-- 这种方法需要知道父元素和子元素的高度，父元素的line-height的值为父元素高度减去子元素高度的一半。-->父元素：position:relative;子元素：positon:absolute;top:50%;transform:translate(0,-50%);
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>垂直居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
position: relative;
top: 0;
left: 0;
}
.child {
width: 300px;
height: 100px;
background: blue;
position: absolute;
top: 50%;
left:0;
transform: translate(0,-50%);
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html>父元素：position:relative;子元素：positon:absolute;top:50%;margin-top:-子元素高度的一半;
父元素：display:flex;align-items:center;
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>垂直居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
display: flex;
align-items: center;
}
.child {
width: 300px;
height: 100px;
background: blue;
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html>父元素：display:table-cell;vertical-align:middle;text-align:center;
子元素；display:inline-block;
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>垂直居中1</title>
<style>
.parent {
width: 500px;
height: 400px;
background: red;
display:table-cell;
vertical-align:middle;
text-align:center;
}
.child {
width: 300px;
height: 100px;
background: blue;
display: inline-block;
}
</style>
</head>
<body>
<p class="parent">
<p class="child"></p>
</p>
</body>
</html>父元素：position:relative;
子元素：position:absolute