我无法弄清楚为什么我的第三个下拉菜单无效，前两个下拉菜单在桌面设备，平板电脑和移动设备上大小调整，但第三个下拉菜单仅适用于桌面，但不适用于移动。任何帮助将不胜感激。这是我的导航菜单HTML代码：
.toggle,
[id^=drop] {
display: none;
}
/* Giving a background-color to the nav container. */
nav {
margin:0;
padding: 0;
background-color: #000000;
}
/* Since we'll have the "ul li" "float:left"
* we need to add a clear after the container. */
nav:after {
content:"";
display:table;
clear:both;
}
/* Removing padding, margin and "list-style" from the "ul",
* and adding "position:reltive" */
nav ul {
display: flex;
justify-content: center;
padding:0;
margin:0;
list-style: none;
position: relative;
}
/* Positioning the navigation items inline */
nav ul li {
margin: 0px;
display:inline-block;
float: left;
background-color: #000000;
}
/* Styling the links */
nav a {
display:block;
padding:14px 20px;
color:#FFF;
font-size:17px;
text-decoration:none;
line-height: 32px;
}
nav ul li ul li:hover { background: #000000; }
/* Background color change on Hover */
nav a:hover {
background-color: #FFC213;
}
/* Hide Dropdowns by Default
* and giving it a position of absolute */
nav ul ul {
display: none;
position: absolute;
/* has to be the same number as the "line-height" of "nav a" */
top: 60px;
}
/* Display Dropdowns on Hover */
nav ul li:hover > ul {
display:inherit;
z-index: 3;
}
/* Fisrt Tier Dropdown */
nav ul ul li {
width:170px;
float:none;
display:list-item;
position: relative;
}
/* Second, Third and more Tiers
* We move the 2nd and 3rd etc tier dropdowns to the left
* by the amount of the width of the first tier.
*/
nav ul ul ul li {
position: relative;
top:-60px;
/* has to be the same number as the "width" of "nav ul ul li" */
left:170px;
}
/* Change ' +' in order to change the Dropdown symbol */
li > a:after { content: ' +'; }
li > a:only-child:after { content: ''; }
/* Media Queries
--------------------------------------------- */
@media all and (max-width : 768px) {
nav {
margin: 0;
}
/* Hide the navigation menu by default */
/* Also hide the */
.toggle + a,
.menu {
display: none;
}
/* Stylinf the toggle lable */
.toggle {
display: block;
background-color: #000000;
padding:14px 20px;
color:#FFF;
font-size:17px;
text-decoration:none;
border:none;
}
.toggle:hover {
background-color: #FFC213;
}
/* Display Dropdown when clicked on Parent Lable */
[id^=drop]:checked + ul {
display: block;
}
/* Change menu item's width to 100% */
nav ul li {
display: block;
width: 100%;
}
nav ul ul .toggle,
nav ul ul a {
padding: 0 40px;
}
nav ul ul ul a {
padding: 0 80px;
}
nav a:hover,
nav ul ul ul a {
background-color: #FFC213;
}
nav ul li ul li .toggle,
nav ul ul a,
nav ul ul ul a{
padding:14px 20px;
color:#FFF;
font-size:17px;
}
nav ul li ul li .toggle,
nav ul ul a {
background-color: #212121;
}
/* Hide Dropdowns by Default */
nav ul ul {
float: none;
position:static;
color: #ffffff;
/* has to be the same number as the "line-height" of "nav a" */
}
/* Hide menus on hover***********effect changes on mobile review */
nav ul ul li:hover > ul,
nav ul li:hover > ul {
display: none;
/*****mobile dorpdown code*********z-index:0;***********/
}
/* Fisrt Tier Dropdown */
nav ul ul li {
display: block;
width: 100%;
}
nav ul ul ul li {
position: static;
/* has to be the same number as the "width" of "nav ul ul li" */
}
}
@media all and (max-width : 150px) {
nav ul li {
display:block;
width: 94%;
}
}<nav>
<label for="drop" class="toggle">Menu</label>
<input type="checkbox" id="drop" />
<ul class="menu">
<li><a href="index.html">Home</a></li>
<li>
<!-- First Tier Drop Down -->
<label for="drop-1" class="toggle">About Us +</label>
<a href="About us.html">About Us</a>
<input type="checkbox" id="drop-1" />
<ul>
<li><a href="methodology">Methodology</a></li>
</ul>
</li>
<li><a href="service.html">Services</a></li>
<li>
<!-- First Tier Drop Down -->
<label for="drop-2" class="toggle">List of Courses +</label>
<a href="#">List of Courses</a>
<input type="checkbox" id="drop-2" />
<ul>
<li><a href="administration.html">Administration</a></li>
<li><a href="agriculture.html">Agriculture</a></li>
</ul>
</li>
<li>
<!-- First Tier Drop Down -->
<label for="drop-2" class="toggle">Ongoing Courses +</label>
<a href="#">Ongoing Courses</a>
<input type="checkbox" id="drop-2" />
<ul>
<li><a href="creative.html">Creative</a></li>
<li><a href="enterprise.html">Enterprise</a></li>
<li><a href="microsoft_office.html">Microsoft excel</a></li>
<li><a href="Hardware.html">Hardware</a></li>
<li><a href="management.html">Management</a></li>
<li><a href="microsoft_office.html">Microsoft Office</a></li>
<li><a href="networking.html">Networking</a></li>
<li><a href="webdesign.html">Web design</a></li>
<li><a href="webdev.html">Web development</a></li>
</ul>
</li>
<li><a href="events.html">Events</a></li>
<li><a href="contact.html">Contact</a></li>
<li>
<a href="#"><img src="images/soc/facebook1.png" height="32" width="32"></a>
</li>
<li>
<a href="#"><img src="images/soc/twitter1.png" height="32" width="32"></a>
</li>
<li>
<a href="#"><img src="images/soc/instagram1.png" height="32" width="34"></a>
</li>
</ul>
</nav>
答案 0 :(得分：0)
您正在使用＆＃34; drop-2＆＃34;对于第二次和第三次下拉。对于第三个菜单，将其更改为for="drop-3"和id="drop-3"，它将起作用。
.toggle,
[id^=drop] {
display: none;
}
/* Giving a background-color to the nav container. */
nav {
margin:0;
padding: 0;
background-color: #000000;
}
/* Since we'll have the "ul li" "float:left"
* we need to add a clear after the container. */
nav:after {
content:"";
display:table;
clear:both;
}
/* Removing padding, margin and "list-style" from the "ul",
* and adding "position:reltive" */
nav ul {
display: flex;
justify-content: center;
padding:0;
margin:0;
list-style: none;
position: relative;
}
/* Positioning the navigation items inline */
nav ul li {
margin: 0px;
display:inline-block;
float: left;
background-color: #000000;
}
/* Styling the links */
nav a {
display:block;
padding:14px 20px;
color:#FFF;
font-size:17px;
text-decoration:none;
line-height: 32px;
}
nav ul li ul li:hover { background: #000000; }
/* Background color change on Hover */
nav a:hover {
background-color: #FFC213;
}
/* Hide Dropdowns by Default
* and giving it a position of absolute */
nav ul ul {
display: none;
position: absolute;
/* has to be the same number as the "line-height" of "nav a" */
top: 60px;
}
/* Display Dropdowns on Hover */
nav ul li:hover > ul {
display:inherit;
z-index: 3;
}
/* Fisrt Tier Dropdown */
nav ul ul li {
width:170px;
float:none;
display:list-item;
position: relative;
}
/* Second, Third and more Tiers
* We move the 2nd and 3rd etc tier dropdowns to the left
* by the amount of the width of the first tier.
*/
nav ul ul ul li {
position: relative;
top:-60px;
/* has to be the same number as the "width" of "nav ul ul li" */
left:170px;
}
/* Change ' +' in order to change the Dropdown symbol */
li > a:after { content: ' +'; }
li > a:only-child:after { content: ''; }
/* Media Queries
--------------------------------------------- */
@media all and (max-width : 768px) {
nav {
margin: 0;
}
/* Hide the navigation menu by default */
/* Also hide the */
.toggle + a,
.menu {
display: none;
}
/* Stylinf the toggle lable */
.toggle {
display: block;
background-color: #000000;
padding:14px 20px;
color:#FFF;
font-size:17px;
text-decoration:none;
border:none;
}
.toggle:hover {
background-color: #FFC213;
}
/* Display Dropdown when clicked on Parent Lable */
[id^=drop]:checked + ul {
display: block;
}
/* Change menu item's width to 100% */
nav ul li {
display: block;
width: 100%;
}
nav ul ul .toggle,
nav ul ul a {
padding: 0 40px;
}
nav ul ul ul a {
padding: 0 80px;
}
nav a:hover,
nav ul ul ul a {
background-color: #FFC213;
}
nav ul li ul li .toggle,
nav ul ul a,
nav ul ul ul a{
padding:14px 20px;
color:#FFF;
font-size:17px;
}
nav ul li ul li .toggle,
nav ul ul a {
background-color: #212121;
}
/* Hide Dropdowns by Default */
nav ul ul {
float: none;
position:static;
color: #ffffff;
/* has to be the same number as the "line-height" of "nav a" */
}
/* Hide menus on hover***********effect changes on mobile review */
nav ul ul li:hover > ul,
nav ul li:hover > ul {
display: none;
/*****mobile dorpdown code*********z-index:0;***********/
}
/* Fisrt Tier Dropdown */
nav ul ul li {
display: block;
width: 100%;
}
nav ul ul ul li {
position: static;
/* has to be the same number as the "width" of "nav ul ul li" */
}
}
@media all and (max-width : 150px) {
nav ul li {
display:block;
width: 94%;
}
}<nav>
<label for="drop" class="toggle">Menu</label>
<input type="checkbox" id="drop" />
<ul class="menu">
<li><a href="index.html">Home</a></li>
<li>
<!-- First Tier Drop Down -->
<label for="drop-1" class="toggle">About Us +</label>
<a href="About us.html">About Us</a>
<input type="checkbox" id="drop-1" />
<ul>
<li><a href="methodology">Methodology</a></li>
</ul>
</li>
<li><a href="service.html">Services</a></li>
<li>
<!-- First Tier Drop Down -->
<label for="drop-3" class="toggle">List of Courses +</label>
<a href="#">List of Courses</a>
<input type="checkbox" id="drop-3" />
<ul>
<li><a href="administration.html">Administration</a></li>
<li><a href="agriculture.html">Agriculture</a></li>
</ul>
</li>
<li>
<!-- First Tier Drop Down -->
<label for="drop-2" class="toggle">Ongoing Courses +</label>
<a href="#">Ongoing Courses</a>
<input type="checkbox" id="drop-2" />
<ul>
<li><a href="creative.html">Creative</a></li>
<li><a href="enterprise.html">Enterprise</a></li>
<li><a href="microsoft_office.html">Microsoft excel</a></li>
<li><a href="Hardware.html">Hardware</a></li>
<li><a href="management.html">Management</a></li>
<li><a href="microsoft_office.html">Microsoft Office</a></li>
<li><a href="networking.html">Networking</a></li>
<li><a href="webdesign.html">Web design</a></li>
<li><a href="webdev.html">Web development</a></li>
</ul>
</li>
<li><a href="events.html">Events</a></li>
<li><a href="contact.html">Contact</a></li>
<li>
<a href="#"><img src="images/soc/facebook1.png" height="32" width="32"></a>
</li>
<li>
<a href="#"><img src="images/soc/twitter1.png" height="32" width="32"></a>
</li>
<li>
<a href="#"><img src="images/soc/instagram1.png" height="32" width="34"></a>
</li>
</ul>
</nav>