css - 如果窗口高度缩小，我有一个图像将主体推离 html 元素

Question

我正在构建一个网站，主页上 256X480 的图片脱离了主体并将主体推离 html 元素，我对如何处理这个图像及其容器有点困惑似乎对 max-height 属性没有任何反应。有人可以解释为什么会这样，或者向我指出一些资源来解释这个问题以及如何解决这个问题，谢谢。

https://jsfiddle.net/9oy5n0he/

html{
    height: 100%;
}
body{
    margin: 0px;
    background-image: linear-gradient( 0, rgba(0,0,0,.8) 30%, rgba(0,150,255,.8) 100%), url("images/mainCover.jpg");
    background-repeat: no-repeat;
    background-size: cover;
    height: 100%;
}
img{
    max-width: 100%;
}
/*nav and header*/
header{
    background-color: rgba(255,165,0,.8);
    display: flex;
    flex-flow: row wrap;
    justify-content: center;
    border-bottom: 8px solid black;
}
nav ul {
        list-style: none;
        padding: 0;
}
header h1{
    text-align: center;
    margin: 0;
    padding: 15px;
    text-shadow: 5px 5px 5px rgba(0,0,0,.3);
}
header h1, nav a{
    font-weight: 700;
    font-family: arial;
}
header nav{
    display: none;
}

.main-nav{
    margin: 4px;
}
nav ul li{ 
    text-align: center;
    margin: 0 4px;
    border: 1px solid white;
    border-radius: 15px;
    font-size: 1.2rem;
}
a{
    text-decoration: none;
}

 nav a:visited, nav a,h1{
   color: white; 
}

.current-page{ 
    background-color: rgba(0,0,0,.5);
}

footer nav{
    position: fixed;
    width: 100%;
    bottom: 0px;
}

footer nav ul{
    margin: 0;
}
footer nav li{
    background-color: rgba(255,165,0,.8);
}
/*home page*/
.bookWrapper{
    width: 25%;
    margin: auto;
}
 .bookLink {
    display: block;
    margin: auto;
}

.bookImage{
    margin: auto;
    display: block;
}

.amazonBookLabel{
    background-color: rgba(0,0,0,.5);
    color: white;
    padding: 10px;
    font-size: 1.5em;
    font-weight: 600;
    width: 50%;
    border-radius: 20px;
    margin: 30px auto;
    text-align: center;
    position: relative;
}
.amazonBookLabel:after{
    content: "";
    width: 30px;
    height: 5px;
    background-color: rgba(0,0,0,.5);
    position: absolute;
    bottom: -5px;
    left: calc(50% - 17px);    
}
.amazonBookLabel:before{
    content: "";
    width: 0;
    height: 0;
    border-left:  40px solid rgba(0,0,0,.5);
    border-top: 40px solid transparent;
    position: absolute;
    bottom: -45px;
    transform: rotate(-45deg);
    transform-origin: top left;
    left: calc(50% - 30px);
}

/***responsive***/
@media screen and (min-width: 400px){
        header{
            height: 130px;
            display: flex;
            justify-content: center;
        }
      header h1{
                font-size: 2em;
                align-self: flex-start;
                white-space: nowrap;
                border: 8px solid black;
            }
     header nav{
                display: block;
                align-self: flex-end;
            }
      .main-nav{
                display: flex;
                justify-content: flex-end;
            }
     .main-nav li{
                border-radius: 8px;
                padding: 5px;
                font-size: 1.3rem;
            }
    .characters:hover {
            position: relative;
            border-radius: 8px 8px 0 0;
            }

     .drop-menu{
            position: absolute;
            visibility: hidden;
            display: block;
            top: 33px;
            white-space: nowrap;
            left: -2px;
            background-color: rgba(255,165,0,.8);
            border: 1px solid rgba(0,0,0,.02);
            box-shadow: 5px 5px 5px 2px rgba(0,0,0,.3);
            opacity: 0;
            transition: opacity 300ms ease-in-out 0s;
            z-index: 1;
            }
    .characters:hover .drop-menu{
             visibility: visible;
             opacity:1;
        }

    .drop-menu li{
        margin: 0;
        border-radius: 0;
    } 

    footer nav{
                display: none;
            }
}
@media screen and (min-width:860px){
    header{
        height: 120px;
        justify-content: space-between;
    }
    header h1{
        margin: 0 0 0 20px;
    }
    .main-nav li{
        font-size: 1.5rem;
    }
    header nav{
        margin: 0 40px 0 0;
    }
}    

@media screen and (min-width: 1109px){
    header h1{
        font-size: 3em;
        margin: 0 0 0 80px;
    }
    .main-nav > li{
        margin: 0 8px;
    }
    header nav{
        margin: 0 80px 0 0;
    }
}

Answer 1

这是因为 html 上的 height: 100% 限制了高度，从技术上讲图像溢出了 html/body，所以你不会看到溢出的背景.

更好的技术是删除 html 上的 height(不是必需的)并在 body 上使用 min-height: 100vh

body {
  margin: 0px;
  background-image: linear-gradient( 0, rgba(0, 0, 0, .8) 30%, rgba(0, 150, 255, .8) 100%), url("images/mainCover.jpg");
  background-repeat: no-repeat;
  background-size: cover;
  min-height: 100vh;
}

img {
  max-width: 100%;
}


/*nav and header*/

header {
  background-color: rgba(255, 165, 0, .8);
  display: flex;
  flex-flow: row wrap;
  justify-content: center;
  border-bottom: 8px solid black;
}

nav ul {
  list-style: none;
  padding: 0;
}

header h1 {
  text-align: center;
  margin: 0;
  padding: 15px;
  text-shadow: 5px 5px 5px rgba(0, 0, 0, .3);
}

header h1,
nav a {
  font-weight: 700;
  font-family: arial;
}

header nav {
  display: none;
}

.main-nav {
  margin: 4px;
}

nav ul li {
  text-align: center;
  margin: 0 4px;
  border: 1px solid white;
  border-radius: 15px;
  font-size: 1.2rem;
}

a {
  text-decoration: none;
}

nav a:visited,
nav a,
h1 {
  color: white;
}

.current-page {
  background-color: rgba(0, 0, 0, .5);
}

footer nav {
  position: fixed;
  width: 100%;
  bottom: 0px;
}

footer nav ul {
  margin: 0;
}

footer nav li {
  background-color: rgba(255, 165, 0, .8);
}


/*home page*/

.bookWrapper {
  width: 25%;
  margin: auto;
}

.bookLink {
  display: block;
  margin: auto;
}

.bookImage {
  margin: auto;
  display: block;
}

.amazonBookLabel {
  background-color: rgba(0, 0, 0, .5);
  color: white;
  padding: 10px;
  font-size: 1.5em;
  font-weight: 600;
  width: 50%;
  border-radius: 20px;
  margin: 30px auto;
  text-align: center;
  position: relative;
}

.amazonBookLabel:after {
  content: "";
  width: 30px;
  height: 5px;
  background-color: rgba(0, 0, 0, .5);
  position: absolute;
  bottom: -5px;
  left: calc(50% - 17px);
}

.amazonBookLabel:before {
  content: "";
  width: 0;
  height: 0;
  border-left: 40px solid rgba(0, 0, 0, .5);
  border-top: 40px solid transparent;
  position: absolute;
  bottom: -45px;
  transform: rotate(-45deg);
  transform-origin: top left;
  left: calc(50% - 30px);
}


/***responsive***/

@media screen and (min-width: 400px) {
  header {
    height: 130px;
    display: flex;
    justify-content: center;
  }
  header h1 {
    font-size: 2em;
    align-self: flex-start;
    white-space: nowrap;
    border: 8px solid black;
  }
  header nav {
    display: block;
    align-self: flex-end;
  }
  .main-nav {
    display: flex;
    justify-content: flex-end;
  }
  .main-nav li {
    border-radius: 8px;
    padding: 5px;
    font-size: 1.3rem;
  }
  .characters:hover {
    position: relative;
    border-radius: 8px 8px 0 0;
  }
  .drop-menu {
    position: absolute;
    visibility: hidden;
    display: block;
    top: 33px;
    white-space: nowrap;
    left: -2px;
    background-color: rgba(255, 165, 0, .8);
    border: 1px solid rgba(0, 0, 0, .02);
    box-shadow: 5px 5px 5px 2px rgba(0, 0, 0, .3);
    opacity: 0;
    transition: opacity 300ms ease-in-out 0s;
    z-index: 1;
  }
  .characters:hover .drop-menu {
    visibility: visible;
    opacity: 1;
  }
  .drop-menu li {
    margin: 0;
    border-radius: 0;
  }
  footer nav {
    display: none;
  }
}

@media screen and (min-width:860px) {
  header {
    height: 120px;
    justify-content: space-between;
  }
  header h1 {
    margin: 0 0 0 20px;
  }
  .main-nav li {
    font-size: 1.5rem;
  }
  header nav {
    margin: 0 40px 0 0;
  }
}

@media screen and (min-width: 1109px) {
  header h1 {
    font-size: 3em;
    margin: 0 0 0 80px;
  }
  .main-nav > li {
    margin: 0 8px;
  }
  header nav {
    margin: 0 80px 0 0;
  }
}

<main>
  <header>
    <h1>Seraph Chronicles</h1>
    <nav>
      <ul class="main-nav">
        <li class="main-nav-item current-page"><a href="index.html">Home</a></li>
        <li class="main-nav-item"><a href="about.html">About</a></li>
        <li class="main-nav-item characters">
          <a href="characters.html">Characters</a>
          <ul class="drop-menu">
            <li><a href="ethanClarke.html">Ethan Clarke</a></li>
            <li><a href="serenaKiriaga.html">Serena Kiriaga</a></li>
            <li><a href="MarcusFlynn.html">Marcus Flynn</a></li>
            <li><a href="EmilyAshdown.html">Emily Ashdown</a></li>
            <li><a href="MilesWest.html">Director Miles West</a></li>
          </ul>
        </li>
        <li class="main-nav-item"><a href="auther.html">Author</a></li>
      </ul>
    </nav>
  </header>
  <section>
    <p class="amazonBookLabel">Get the first and newest addition of the trilogy here!</p>
    <div class="bookWrapper">
      <a href="https://www.amazon.com/Seraph-Chronicles-Kyle-James-Feller/dp/1520404999/ref=sr_1_3?ie=UTF8&qid=1496613120&sr=8-3&keywords=seraph+chronicles" class="bookLink">
        <img class="bookImage" src="images/bookCover.jpg" alt="image of seraph chronicles: evangelion for purchase">
      </a>
    </div>
  </section>
  <footer>
  </footer>
  <section>
  </section>
  <footer>
    <nav>
      <ul>
        <li><a href="index.html">Home</a></li>
        <li><a href="about.html">About</a></li>
        <li><a href="characters.html">Characters</a></li>
        <li><a href="auther.html">Author</a></li>
      </ul>
    </nav>
  </footer>
</main>