我想要做的是将文本(以及将并排或位于文本顶部的图像)居中，但命令 justify-content:center 对我不起作用。它水平居中但不是垂直居中。你能告诉我哪里出了问题吗？我实际上是一个初学者，这是我的第一个网站。
代码如下:
body {
font-family: Gotham A,Gotham B,Helvetica,Arial,sans-serif;
}
h1 {
font-size: 3em;
text-transform:uppercase;
}
h4 {
font-size: 1.5em;
color:#9e9e9e;
}
section {
width: 100%;
display: inline-block;
margin: 0;
max-width: 960;
height:100vh;
vertical-align: middle;
}
#welcome-screen {
width: 100%;
display: table;
margin: 0;
max-width: none;
height:100vh;
background-color:#ebebeb;
padding:0 7%;
}
.heading {
display:table-cell;
vertical-align: middle;
}
.heading-span {
display: block;
color: #8e8e8e;
font-size: 18px;
margin-top: 0px;
text-transform:none;
}
.scrolldown-button {
position: absolute;
display: table;
text-align: center;
bottom: 30px;
left: 0;
right: 0;
margin: 0 auto 0 auto;
width: 48px;
height: 48px;
font-size:20px;
}
a {
color:#000000;
transition: ease-in-out 0.15s
}
a:hover{
color:#fbd505;
}
#content {
width: 100%;
height:100vh;
}
.wrapper {
display: flex;
flex-direction: column;
align-items: center;
justify-content: center;
}
p {
display:column;
vertical-align: middle;
max-width: 960px;
}
.content-heading-span {
display: block;
font-size: 32px;
margin-top: 0px;
text-transform:uppercase;
margin-left:-20px;
}<!DOCTYPE html>
<html >
<head>
<meta charset="UTF-8">
<title>Test</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel='stylesheet prefetch' href='https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css'>
<link rel="stylesheet" href="css/style.css">
<link rel="stylesheet" href="path/to/font-awesome/css/font-awesome.min.css">
<link rel="stylesheet" href="https://cloud.typography.com/6493094/7214972/css/fonts.css">
</head>
<body>
<section id="welcome-screen">
<div class="heading">
<h1><span class="heading-span">Hi! My name is</span>
<strong>John Doe</strong>
</h1>
</div>
<div class="scrolldown-button">
<a href="#content"><span class="glyphicon glyphicon-chevron-down" aria-hidden="true"></span></a>
</div>
</section>
<section>
<div id="content">
<div class="wrapper">
<p><span class="content-heading-span"><strong>O Mnie</strong></span>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin eget bibendum odio, eget varius tortor. Etiam imperdiet, sem in faucibus convallis, justo purus rutrum magna, ut lacinia ex tellus sit amet lectus. Curabitur tempor imperdiet laoreet. Quisque magna magna, tempus a nibh vitae, maximus malesuada mi. Nulla a justo dolor. Nullam risus nisl, vulputate vel arcu id, viverra finibus mauris. Donec porttitor lectus ut augue vehicula, vitae vehicula turpis eleifend. Proin eu quam at odio consectetur tincidunt. Proin eget elit id purus lacinia tincidunt. Nam at urna est. Quisque viverra nisi eu molestie accumsan. Ut at porttitor sem, quis viverra massa. Nulla odio libero, dictum a diam euismod, rhoncus efficitur lectus. Suspendisse eu mi vel diam euismod fermentum at et.</p>
<p><span class="content-heading-span"><strong>O Mnie</strong></span>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin eget bibendum odio, eget varius tortor. Etiam imperdiet, sem in faucibus convallis, justo purus rutrum magna, ut lacinia ex tellus sit amet lectus. Curabitur tempor imperdiet laoreet. Quisque magna magna, tempus a nibh vitae, maximus malesuada mi. Nulla a justo dolor. Nullam risus nisl, vulputate vel arcu id, viverra finibus mauris. Donec porttitor lectus ut augue vehicula, vitae vehicula turpis eleifend. Proin eu quam at odio consectetur tincidunt. Proin eget elit id purus lacinia tincidunt. Nam at urna est. Quisque viverra nisi eu molestie accumsan. Ut at porttitor sem, quis viverra massa. Nulla odio libero, dictum a diam euismod, rhoncus efficitur lectus. Suspendisse eu mi vel diam euismod fermentum at et.</p>
</div>
</div>
</body>
</html>最佳答案
.wrapper 是您的 flex 容器，没有高度设置。添加 height: 100%; 到它并且垂直居中工作。但是，.wrapper 的父级(即 .content)具有 height: 100vh - 如果其内容超出此范围，它将变得一团糟(即重叠)，因此您可能希望将其高度设置更改为 min-height 而不是 height
body {
font-family: Gotham A,Gotham B,Helvetica,Arial,sans-serif;
}
h1 {
font-size: 3em;
text-transform:uppercase;
}
h4 {
font-size: 1.5em;
color:#9e9e9e;
}
section {
width: 100%;
display: inline-block;
margin: 0;
max-width: 960;
height:100vh;
vertical-align: middle;
}
#welcome-screen {
width: 100%;
display: table;
margin: 0;
max-width: none;
height:100vh;
background-color:#ebebeb;
padding:0 7%;
}
.heading {
display:table-cell;
vertical-align: middle;
}
.heading-span {
display: block;
color: #8e8e8e;
font-size: 18px;
margin-top: 0px;
text-transform:none;
}
.scrolldown-button {
position: absolute;
display: table;
text-align: center;
bottom: 30px;
left: 0;
right: 0;
margin: 0 auto 0 auto;
width: 48px;
height: 48px;
font-size:20px;
}
a {
color:#000000;
transition: ease-in-out 0.15s
}
a:hover{
color:#fbd505;
}
#content {
width: 100%;
min-height:100vh;
}
.wrapper {
display: flex;
height: 100%;
flex-direction: column;
align-items: center;
justify-content: center;
}
p {
display:column;
vertical-align: middle;
max-width: 960px;
}
.content-heading-span {
display: block;
font-size: 32px;
margin-top: 0px;
text-transform:uppercase;
margin-left:-20px;
}<!DOCTYPE html>
<html >
<head>
<meta charset="UTF-8">
<title>Test</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel='stylesheet prefetch' href='https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css'>
<link rel="stylesheet" href="css/style.css">
<link rel="stylesheet" href="path/to/font-awesome/css/font-awesome.min.css">
<link rel="stylesheet" href="https://cloud.typography.com/6493094/7214972/css/fonts.css">
</head>
<body>
<section id="welcome-screen">
<div class="heading">
<h1><span class="heading-span">Hi! My name is</span>
<strong>John Doe</strong>
</h1>
</div>
<div class="scrolldown-button">
<a href="#content"><span class="glyphicon glyphicon-chevron-down" aria-hidden="true"></span></a>
</div>
</section>
<section>
<div id="content">
<div class="wrapper">
<p><span class="content-heading-span"><strong>O Mnie</strong></span>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin eget bibendum odio, eget varius tortor. Etiam imperdiet, sem in faucibus convallis, justo purus rutrum magna, ut lacinia ex tellus sit amet lectus. Curabitur tempor imperdiet laoreet. Quisque magna magna, tempus a nibh vitae, maximus malesuada mi. Nulla a justo dolor. Nullam risus nisl, vulputate vel arcu id, viverra finibus mauris. Donec porttitor lectus ut augue vehicula, vitae vehicula turpis eleifend. Proin eu quam at odio consectetur tincidunt. Proin eget elit id purus lacinia tincidunt. Nam at urna est. Quisque viverra nisi eu molestie accumsan. Ut at porttitor sem, quis viverra massa. Nulla odio libero, dictum a diam euismod, rhoncus efficitur lectus. Suspendisse eu mi vel diam euismod fermentum at et.</p>
<p><span class="content-heading-span"><strong>O Mnie</strong></span>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Proin eget bibendum odio, eget varius tortor. Etiam imperdiet, sem in faucibus convallis, justo purus rutrum magna, ut lacinia ex tellus sit amet lectus. Curabitur tempor imperdiet laoreet. Quisque magna magna, tempus a nibh vitae, maximus malesuada mi. Nulla a justo dolor. Nullam risus nisl, vulputate vel arcu id, viverra finibus mauris. Donec porttitor lectus ut augue vehicula, vitae vehicula turpis eleifend. Proin eu quam at odio consectetur tincidunt. Proin eget elit id purus lacinia tincidunt. Nam at urna est. Quisque viverra nisi eu molestie accumsan. Ut at porttitor sem, quis viverra massa. Nulla odio libero, dictum a diam euismod, rhoncus efficitur lectus. Suspendisse eu mi vel diam euismod fermentum at et.</p>
</div>
</div>
</body>
</html>关于html - 证明内容 :center doesn't work，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/41655412/