<!DOCTYPE html>
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.1/dist/css/bootstrap.min.css" rel="stylesheet"
integrity="sha384-+0n0xVW2eSR5OomGNYDnhzAbDsOXxcvSN1TPprVMTNDbiYZCxYbOOl7+AMvyTG2x" crossorigin="anonymous">
</head>
<style type="text/css" href="style.css"></style>
<body>
<nav class="navbar navbar-expand-lg navbar-dark bg-dark">
<div class="container-fluid">
<a class="navbar-brand" href="#">Magic Notes</a>
<button class="navbar-toggler" type="button" data-bs-toggle="collapse"
data-bs-target="#navbarSupportedContent" aria-controls="navbarSupportedContent"
aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav me-auto mb-2 mb-lg-0">
<li class="nav-item">
<a class="nav-link active" aria-current="page" href="#">Home</a>
</li>
</ul>
<form class="d-flex">
<input class="form-control me-2" type="search" placeholder="Search" aria-label="Search">
<button class="btn btn-outline-success" type="submit">Search</button>
</form>
</div>
</div>
</nav>
<div class="container my-3 mx-10" style="max-width:70vw;margin:0 auto;">
<h1>Welcome To Magic Notes</h1>
<div class="card">
<div class="card-body">
<h5 class="card-title">Add a Note</h5>
<textarea class="form-control" id="addTxt" style="height: 100px"></textarea>
<button class="btn btn-primary" style="margin-top:1em;"" id= " addBtn">Add Note</button>
</div>
</div>
<hr>
<h1>Your Notes</h1>
<hr>
<div class="container">
<div>HI</div>
<div>HI</div>
<div>HI</div>
</div>
</div>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.1/dist/js/bootstrap.bundle.min.js"
integrity="sha384-gtEjrD/SeCtmISkJkNUaaKMoLD0//ElJ19smozuHV6z3Iehds+3Ulb9Bn9Plx0x4"
crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/@popperjs/core@2.9.2/dist/umd/popper.min.js"
integrity="sha384-IQsoLXl5PILFhosVNubq5LC7Qb9DXgDA9i+tQ8Zj3iwWAwPtgFTxbJ8NT4GN1R8p"
crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.1/dist/js/bootstrap.min.js"
integrity="sha384-Atwg2Pkwv9vp0ygtn1JAojH0nYbwNJLPhwyoVbhoPwBhjQPR5VtM2+xf0Uwh9KtT"
crossorigin="anonymous"></script>
<!-- <script src="app.js"></script> -->
</body>
在下面的代码中，我只使用了很少的CSS来尝试一些东西(我将在下面添加CSS文件(。然而，我的目标类容器即使在将其更改为flex之后也不会水平显示内容。我已经使用了一些引导程序类，并且对这些东西非常陌生——这种令人费解的行为的可能原因是什么。
CSS代码：
*{
margin:0;
padding: 0;
box-sizing: border-box;}
.container{
display:flex;
flex-direction:row;
flex: 1;}
<style type="text/css" href="style.css"></style>
这是你的问题。连接CSS文件时，需要使用链接标记而不是样式标记。试试这个：
<link rel="stylesheet" href="style.css">