HTML，CSS:无法重新定位我的下拉列表

Question

我正在尝试建立一个网站。但由于某些原因，我无法重新定位我的下拉列表（CSS）。需要一些帮助。我需要把下拉列表移到中间。

HTML代码：

    <header>
        <h1 id="my_cycle_head">MY CYCLE</h1>
        <ul id="main_navbar">
            <li>
                <a href="#" style="margin-left: -40px; z-index: -1">Home</a>
            </li>
            <li class="dropdown">
                <a class="dropbtn" style="margin-left: -40px; z-index: -1">Rent</a>
                <div class="dropdown-content">
                    <a href="#">Mountain Bikes</a>
                    <a href="#">Hybrid Bikes</a>
                    <a href="#">Road Bikes</a>
                    <a href="#">City Bikes</a>
                </div>
            </li>
            <li>
                <a href="faq.html" style="margin-left: -40px; z-index: -1">FAQ's</a>
            </li>
            <li>
                <a href="about.html" style="margin-left: -40px; z-index: -1">About</a>
            </li>
        </ul>
    </header>

CSS代码：

body {
  font-family: 'Open-sans', sans-serif, Helvetica;
  background-color: #f9f9f9;
  text-align: center;
  box-sizing: border-box;
}
.dropdown {
  position: relative;
}
.dropdown-content {
  display: none;
  min-width: 200px;
  right: 1;
  position: absolute;
  box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
}
.dropdown-content a {
  display: block;
}
.dropdown:hover .dropdown-content {
  display: block;
  background-color: #6ab47b;
}
#my_cycle_head {
  text-align: center;
  float: left;
  margin-left: 50px;
  font-weight: normal;
}
#main_navbar {
  text-align: center;
  margin: 0 auto;
  float: right;
  margin-top: 25px;
}
#main_navbar li {
  list-style-type: none;
  display: inline-block;
  min-width: 5em;
}
#main_navbar li a {
  text-decoration: none;
  color: white;
  font-size: 1.2em;
  font-weight: normal;
  text-align: center;
  overflow: hidden;
}
header {
  background-color: #6ab47b;
  height: 95px;
  width: 100%;
  float: left;
  padding-right: 30px;
  margin-left: -20px;
  margin-top: -20px;
  padding-top: 20px;
  color: white;
}

提前谢谢。

Answer 1

您可以将菜单向右浮动。为了集中你的下拉菜单，你应该做以下

• 从所有<a>元素中删除"margin-left: -40px;内联样式
• 在.dropdown-content类中插入以下两行

right: 50%;

transform: translate(50%,0);

Answer 2

在CSS中，下拉列表向右浮动。只要去掉它，Dropdown就会在中心。

#main_navbar {
text-align: center;
margin: 0 auto;
/*float: right;*/
margin-top: 25px;
} 

Answer 3

已接受用你的#main_navbar > li > a: 替换这个css

   #main_navbar > li > a {
        display:inline-block;
        margin-left: 15px;       /* This is when the drop down box appears */
        position: relative;
    }

并将其添加到您的css代码中：

 #main_navbar > li > {
        text-align:center;
 }

Answer 4

尝试下面的代码，它可能会对您有所帮助。

body {
  font-family: 'Open-sans', sans-serif, Helvetica;
  background-color: #f9f9f9;
  text-align: center;
  box-sizing: border-box;
}
header {
  background-color: #6ab47b;
  height: 95px;
  width: 100%;
  float: left;
  padding-right: 30px;
  margin-left: -20px;
  margin-top: -20px;
  padding-top: 20px;
  color: white;
}
#my_cycle_head {
  text-align: center;
  float: left;
  margin-left: 50px;
  font-weight: normal;
}
.dropdown-content {
    position: absolute;
    z-index: 1000;
    display: none;
    float: left;
    min-width: 160px;
    padding: 5px 0;
    margin: 2px 0 0 -50px;
    font-size: 14px;
    text-align: center;
    list-style: none;
    background-color: #6ab47b;
    box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2);
    background-clip: padding-box;
    border: 1px solid #ccc;
    border: 1px solid rgba(0,0,0,.15);
    border-radius: 4px;
    -webkit-box-shadow: 0 6px 12px rgba(0,0,0,.175);
}
#main_navbar{
  float : right;
}
#main_navbar>li {
    float: left;
    padding : 10px;
    list-style-type : none;
}
#main_navbar li a {
  text-decoration: none;
  color: white;
  font-size: 1.2em;
  font-weight: normal;
  text-align: center;
  overflow: hidden;
}
.dropdown>.dropdown-content {
  list-style-type : none;
}
.dropdown>.dropdown-content>li {
  padding : 5px;
  border-bottom : 1px solid #fff;
}
.dropdown>.dropdown-content>li:last-child {
  border-bottom : none;
}
.dropdown>.dropdown-content>li:hover {
  background : white;
  
  color : #6ab47b !important;
}
.dropdown:hover .dropdown-content{
  display : block
}

<header>
  <h1 id="my_cycle_head">MY CYCLE</h1>
  <ul id="main_navbar">
    <li>
      <a href="#">Home</a>
    </li>
     <li class="dropdown">
      <a href="#" class="dropdown-toggle">Rent <span class="caret"></span></a>
      <ul class="dropdown-content">
        <li><a href="#">Mountain Bikes</a></li>
        <li><a href="#">Hybrid Bikes</a></li>
        <li><a href="#">Something else here</a></li>
        <li><a href="#">Road Bikes</a></li>
        <li><a href="#">City Bikes</a></li>
      </ul>
    </li>
    <li><a href="faq.html" >FAQ's</a></li>
    <li><a href="about.html" >About</a>
    </li>
  </ul>
</header>