我正在使用CSS构建我的第一个站点（如果您希望了解此问题，请访问www.craigdoesdata.de），因此，如果这很明显或已经得到解答，我深表歉意（尽管我花了很长时间进行搜索并且找不到答案）。
我正在使用Bootstrap，并已在我的custom.css文件中调整.bg-dark的背景颜色，如下所示：
.bg-dark {
background-color: #21618c !important;
}
此功能适用于台式机，导航栏和页脚等已更改。但是，在移动设备上会显示默认的bg-深色（＃343a40）。当我检查元素时，它们指向_background-variant.scss，它仍然指定：
.bg-dark {
background-color: #343a40 !important;
}
我的custom.css文件最后加载到html的标头中，我认为这意味着它具有优先级，并且确实可以在桌面上使用。但是，这里肯定缺少某些内容，这意味着移动版本没有使用我的custom.css样式表吗？
这是我编写的HTML：
<!doctype html>
<html lang="en">
<head>
<!-- Required meta tags -->
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<!-- Bootstrap CSS -->
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css" integrity="sha384-9aIt2nRpC12Uk9gS9baDl411NQApFmC26EwAOH8WgZl5MYYxFfc+NcPb1dKGj7Sk" crossorigin="anonymous">
<!-- Add icon library -->
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css">
<!-- Custom CSS -->
<link rel="stylesheet" type="text/css" href="css/custom.css">
<title>Craig Does Data | About</title>
</head>
<body>
<!-- Start Navigation -->
<nav class="navbar fixed-top navbar-expand-lg navbar-dark bg-dark fixed-top">
<!-- Start Container -->
<div class="container">
<!-- Nav Brand -->
<a class="navbar-brand" href="index.html">
<img src="img/logo/logo w on blue.png" alt="The logo for Craig Does Data" height="40">
</a>
<!-- Start Button -->
<button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbarResponsive" aria-controls="navbarResponsive" aria-expanded="false" aria-label="Toggle Navigation">
<span class="navbar-toggler-icon"></span>
</button>
<!-- End Button -->
<!-- Start Links -->
<div class="collapse navbar-collapse" id="navbarResponsive">
<ul class="navbar-nav ml-auto">
<!-- Home -->
<li class="nav-item">
<a class="nav-link" href=index.html>Home</a>
</li>
<!-- Services -->
<li class="nav-item">
<a class="nav-link" href=blog.html>Blog</a>
</li>
<!-- Portfolio -->
<li class="nav-item">
<a class="nav-link" href=projects.html>Projects</a>
</li>
<!-- About -->
<li class="nav-item">
<a class="nav-link" href=about.html>About</a>
</li>
<!-- Contact -->
<li class="nav-item">
<a class="nav-link" href=contact.html>Contact</a>
</li>
</ul>
</div>
<!-- End Links -->
</div>
</nav>
<!-- End Navigation -->
<!-- Start Container -->
<div class="container">
</div>
<!-- End Container -->
<br>
<!-- Footer -->
<footer class="py-5 bg-dark">
<div class="container">
<p class="m-0 text-center text-white">Copyright © Craig Dickson 2020</p>
<!--Twitter-->
<div align="center">
<a href="http://www.twitter.com/craigdoesdata" target="_blank" class="fa fa-twitter"></a>
<!--GitHub-->
<a href="https://github.com/thecraigd" target="_blank" class="fa fa-github"></a>
<!--Medium-->
<a href="https://medium.com/@thecraigdickson" target="_blank" class="fa fa-medium"></a>
<!--LinkedIn-->
<a href="https://www.linkedin.com/in/dicksoncraig/" target="_blank" class="fa fa-linkedin"></a>
</div>
</div>
</footer>
<!-- Optional JavaScript -->
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src="https://code.jquery.com/jquery-3.5.1.slim.min.js" integrity="sha384-DfXdz2htPH0lsSSs5nCTpuj/zy4C+OGpamoFVy38MVBnE+IbbVYUew+OrCXaRkfj" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/js/bootstrap.min.js" integrity="sha384-OgVRvuATP1z7JjHLkuOU7Xw704+h835Lr+6QL9UvYjZE3Ipu6Tp75j7Bh/kR0JKI" crossorigin="anonymous"></script>
</body>
</html>
这里是custom.css
/* Start Global Styles */
body {
padding: 1em;
}
@media (min-width: 992px) {
body{
padding-top: 56px;
}
.carousel-item {
height: 65vh;
min-height: 300px;
background: no-repeat center center scroll;
-webkit-background-size: cover;
-moz-background-size: cover;
-o-background-size: cover;
background-size: cover;
}
.portfolio-item {
margin-bottom:30px;
}
/* End Global Styles */
/* My colour palette (from htmlcolorcodes.com) */
/* color-4 is my primary, color-3 for hovers */
.color-1 {color: #d2b4de;}
.color-2 {color: #5b2c6f;}
.color-3 {color: #aed6f1;}
.color-4 {color: #21618c;}
.color-5 {color: #76d7c4;}
.color-6 {color: #117864;}
/* Navigation Background Colour */
.bg-dark {
background-color: #21618c !important;
}
/* Call to Action ('Contact me' on index.html) Button State */
.btn-secondary {
color: #fff;
background-color: #21618c;
border-color: #21618c;
}
.btn-secondary:hover {
color: #fff;
background-color: #5499c7;
border-color: #5499c7;
}
/* Button Hover State */
.btn-primary:hover {
color: #fff;
background-color: #5499c7;
border-color: #5499c7;
}
/* Button normal state */
.btn-primary {
color: #fff;
background-color: #21618c;
border-color: #21618c;
}
/* Nav Link Colour */
.navbar-dark .navbar-nav .nav-link:focus, .navbar-dark .navbar-nav .nav-link:hover {
color: white;
}
.navbar-dark .navbar-nav .nav-link {
color: black;
}
感谢您的帮助！
您拥有媒体查询中的样式。例如，看看这个
@media (min-width: 992px)
.btn-secondary {
color: #fff;
background-color: #21618c;
border-color: #21618c;
}
因此，当设备宽度小于992px时，它采用默认颜色值而不是您覆盖的值