Middle Div不会成为其他div的中心

Question

我正在尝试创建我的header。其中包括徽标（左），横幅（中）和导航栏（右）。我可以让他们彼此保持水平，但不能让横幅完全坐在页面的中央。

横幅向右推，横过屏幕大约70%。

关于为什么会发生这种情况的任何想法？

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#header1 {
  position: absolute;
  width: 100%;
  height: 100px;
  text-align: center;
  margin: 0px;
  padding-top: 2px;
  padding-right: 2px;
  padding-left: 2px;
  padding-bottom: 2px;
  color: white;
  font-size: 18px;
  background-image: url(content/structure/fmabannerbehind.jpg);
  background-position: center;
  font-family: Constantia, "Lucida Bright", "DejaVu Serif", Georgia, serif;
  font-style: italic;
}
#logo {
  margin-left: 0px;
  height: 100px;
  width: 200px;
  float: left;
  border-color: red;
  border-width: 3px;
  border-style: solid;
}
#logo img {
  height: 100px;
  width: auto;
}
#banner {
  position: absolute;
  height: 100px;
  width: auto;
  display: inline-block;
  margin: 0 auto;
  border-color: red;
  border-width: 3px;
  border-style: solid;
}
#banner img {
  height: 100px;
  width: auto;
}
#menu1 {
  margin-right: 0px;
  height: 100px;
  width: auto;
  float: right;
  border-color: red;
  border-width: 3px;
  border-style: solid;
}

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<div id="header1">
  <div id="logo">
    <a href="http://www.fmarchived.com">
      <img src="/content/structure/logo3.jpg" alt="logo">
    </a>
  </div>
  <div id="banner">
    <a href="/">
      <img src="/content/structure/fmabanneronly.jpg" alt="banner">
    </a>
  </div>
  <div id="menu1">
    <div class="child2menu">
      <ul>
        <li><a href="/aboutus/">About Us</a>
        </li>
        <li><a href="https://www.facebook.com/fmarchived/">Facebook</a>
        </li>
        <li><a href="https://twitter.com/fmarchived">Twitter</a>
        </li>
        <li><a href="https://www.youtube.com/channel/UCOA0NFV-DuoqCRFT3YzBzRg">Youtube</a>
        </li>
      </ul>
    </div>
  </div>
</div>

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Answer 1

<强>更新

  

也许我应该更好地解释，我希望横幅是中心   整个页面，无论其他div正在做什么

然后将position:relative添加到#header1和position:absolute + display: inline-table; position:absolute; left:0; right:0;   两个片段中的margin:auto;到#banner

选项＃1 - 使用CSS flexbox

使用justify-content: space-between中的flexbox，您可以执行此操作，并简化您的代码

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* {
  box-sizing: border-box;
  margin: 0
}
#header1 {
  display: flex;
  justify-content: space-between;
  position: relative
}
#header1 > div {
  border: solid red
}
img {
  vertical-align: bottom
}
#banner {
  display: inline-table;
  position: absolute;
  left: 0;
  right: 0;
  margin: auto;
}

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<div id="header1">
  <div id="logo">
    <a href="http://www.fmarchived.com">
      <img src="//lorempixel.com/200/100" alt="logo">
    </a>
  </div>
  <div id="banner">
    <a href="/">
      <img src="//lorempixel.com/100/100" alt="banner">
    </a>
  </div>
  <div id="menu1">
    <div class="child2menu">
      <ul>
        <li><a href="/aboutus/">About Us</a>
        </li>
        <li><a href="https://www.facebook.com/fmarchived/">Facebook</a>
        </li>
        <li><a href="https://twitter.com/fmarchived">Twitter</a>
        </li>
        <li><a href="https://www.youtube.com/channel/UCOA0NFV-DuoqCRFT3YzBzRg">Youtube</a>
        </li>
      </ul>
    </div>
  </div>
</div>

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选项＃2 - 使用您当前的代码

将position:absolute从#header1更改为relative以删除滚动条

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* {
  box-sizing: border-box;
  margin: 0
}
#header1 {
  position: relative;
  width: 100%;
  height: 100px;
  text-align: center;
  margin: 0;
  padding: 2px;
  color: white;
  font-size: 18px;
  background-image: url(content/structure/fmabannerbehind.jpg);
  background-position: center;
  font-family: Constantia, "Lucida Bright", "DejaVu Serif", Georgia, serif;
  font-style: italic;
}
#header1 > div {
  border: 3px solid red
}
img {
  height: 100px;
  width: auto;
  vertical-align:bottom
}
#logo {
  margin-left: 0;
  width: 200px;
  float: left;
}
#banner {
  width: auto;
  display: inline-table;
  position:absolute;
  left:0;
  right:0;
  margin:auto;

    
}
#menu1 {
  margin-right: 0px;
  float: right;
}

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<div id="header1">
  <div id="logo">
    <a href="http://www.fmarchived.com">
      <img src="//lorempixel.com/100/100" alt="logo">
    </a>
  </div>
  <div id="banner">
    <a href="/">
      <img src="//lorempixel.com/100/100" alt="banner">
    </a>
  </div>
  <div id="menu1">
    <div class="child2menu">
      <ul>
        <li><a href="/aboutus/">About Us</a>
        </li>
        <li><a href="https://www.facebook.com/fmarchived/">Facebook</a>
        </li>
        <li><a href="https://twitter.com/fmarchived">Twitter</a>
        </li>
        <li><a href="https://www.youtube.com/channel/UCOA0NFV-DuoqCRFT3YzBzRg">Youtube</a>
        </li>
      </ul>
    </div>
  </div>
</div>

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Answer 2

从#banner div中删除position: absolute属性。如果#banner div由于某种原因需要绝对定位，您可以通过给它一个宽度和相应的left属性来使其居中。

Answer 3

只需移除绝对位置，它就会与中心对齐。

#banner {
  /*position:absolute;*/
  height: 100px;
  width: auto;
  display: inline-block;
  margin:0 auto;
  border-color: red;
  border-width: 3px;
  border-style: solid;
}

Answer 4

你可以使用coordonates和margin：auto;如果使用绝对的话，使你的盒子居中。但你需要重置显示。

#banner {
  position: absolute;
  height: 100px;
  width: auto;
  display: table;/* shrinks on content */
  left:0;
  right:0;
  margin: 0 auto;/* will center in between coordonates if boxe smaller */
  border-color: red;
  border-width: 3px;
  border-style: solid;
}

运行代码片段：

#header1 {
  position: absolute;
  width: 100%;
  height: 100px;
  text-align: center;
  margin: 0px;
  padding-top: 2px;
  padding-right: 2px;
  padding-left: 2px;
  padding-bottom: 2px;
  color: white;
  font-size: 18px;
  background-image: url(content/structure/fmabannerbehind.jpg);
  background-position: center;
  font-family: Constantia, "Lucida Bright", "DejaVu Serif", Georgia, serif;
  font-style: italic;
  background:linear-gradient(to right,gray 50%, lightgray 50%);
}
#logo {
  margin-left: 0px;
  height: 100px;
  width: 200px;
  float: left;
  border-color: red;
  border-width: 3px;
  border-style: solid;
}
#logo img {
  height: 100px;
  width: auto;
}
#banner {
  position: absolute;
  height: 100px;
  width: auto;
  display: table;
  margin: 0 auto;
  left:0;
  right:0;
  border-color: red;
  border-width: 3px;
  border-style: solid;
}
#banner img {
  height: 100px;
  width: auto;
}
#menu1 {
  margin-right: 0px;
  height: 100px;
  width: auto;
  float: right;
  border-color: red;
  border-width: 3px;
  border-style: solid;
}

<div id="header1">
  <div id="logo">
    <a href="http://www.fmarchived.com">
      <img src="/content/structure/logo3.jpg" alt="logo">
    </a>
  </div>
  <div id="banner">
    <a href="/">
      <img src="/content/structure/fmabanneronly.jpg" alt="banner">
    </a>
  </div>
  <div id="menu1">
    <div class="child2menu">
      <ul>
        <li><a href="/aboutus/">About Us</a>
        </li>
        <li><a href="https://www.facebook.com/fmarchived/">Facebook</a>
        </li>
        <li><a href="https://twitter.com/fmarchived">Twitter</a>
        </li>
        <li><a href="https://www.youtube.com/channel/UCOA0NFV-DuoqCRFT3YzBzRg">Youtube</a>
        </li>
      </ul>
    </div>
  </div>
</div>