固定头部底部布局技巧：CSS定位应用详解

<header class="header">头部内容</header>
<main class="main-content">页面主体</main>
<footer class="footer">底部内容</footer>

.header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 60px;
  background: #333;
  color: white;
  z-index: 1000;
}
<p>.footer {
position: fixed;
bottom: 0;
left: 0;
width: 100%;
height: 40px;
background: #666;
color: white;
z-index: 1000;
}</p><p>.main-content {
margin-top: 60px; /<em> 避免内容被头部遮挡 </em>/
margin-bottom: 40px; /<em> 避免内容被底部遮挡 </em>/
min-height: calc(100vh - 100px); /<em> 视口高度减去头尾高度 </em>/
}</p>

<style>
  body, html {
    margin: 0;
    padding: 0;
    font-family: Arial, sans-serif;
  }
  .header {
    position: fixed;
    top: 0;
    width: 100%;
    height: 60px;
    background: #1e90ff;
    color: white;
    text-align: center;
    line-height: 60px;
    z-index: 1000;
  }
  .footer {
    position: fixed;
    bottom: 0;
    width: 100%;
    height: 50px;
    background: #333;
    color: white;
    text-align: center;
    line-height: 50px;
    z-index: 1000;
  }
  .main-content {
    margin: 60px 0 50px 0;
    min-height: calc(100vh - 110px);
    padding: 20px;
    box-sizing: border-box;
  }
</style>
<p><header class="header">固定头部</header>
<main class="main-content">
<p>这里是页面主要内容...</p>
</main>
<footer class="footer">固定底部</footer></p>