javascript - Div 元素在 CSS 之后不显示

Question

Web 开发新手，我正在创建一个新网站，目前使用 html、js 和 css，但在应用 css 后缺少某些元素？ 两个 div 元素 box1 和 box2 都丢失了。我在 chrome 中打开检查选项，看到它们在代码中但没有加载？

<header>
  <img src="SAGE LOGO.png">

  <nav>
    <ul>
      <li><a href="#">Home</a></li>
      <li><a href="#">Help</a></li>
    </ul>
  </nav>
</header>
<main>
  <div class="box1">
    <label class="ld-label">
            Project Number:
          </label>
    <input class="ld-url-input" type="text" id="fetchURL" />
    <button type="button" id="add" class="design_button add">Draw</button>
  </div>
  <div class="box2">
    <form method="post" action="data.php">
      <label class="ld-label">
                  Add Project:
                </label>
      <input class="ld-url-input" type="text" name="textdata">
      <input type="submit" name="submit" value="Submit">
    </form>
  </div>
</main>

<div id="super">
  <div id="container">
  </div>
</div>

CSS:

header img {
  height: 80px;
}

body {
  height: 125vh;
  background-color: #222641;
  background-size: cover;
  font-family: sans-serif;
}

main {
  color: white;
}

header {
  background-color: #A80B16;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 80px;
}

.ld-label {
  width: 200px;
}

.ld-url-input {
  display: inline-block;
}

Answer 1

您的 header 与您的内容重叠。

为 header 移除 position: fixed; 或为 main 提供 padding-top: 80px;

header img {
  height: 80px;
}

body {
  background-color: #222641;
  background-size: cover;
  font-family: sans-serif;
}

main {
  color: white;
  padding-top: 80px;
}

header {
  background-color: #A80B16;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 80px;
}

.ld-label {
  width: 200px;
}

.ld-url-input {
  display: inline-block;
}

<header>
  <img src="SAGE LOGO.png">

  <nav>
    <ul>
      <li><a href="#">Home</a></li>
      <li><a href="#">Help</a></li>
    </ul>
  </nav>
</header>
<main>
  <div class="box1">
    <label class="ld-label">
        Project Number:
      </label>
    <input class="ld-url-input" type="text" id="fetchURL" />
    <button type="button" id="add" class="design_button add">Draw</button>
  </div>
  <div class="box2">
    <form method="post" action="data.php">
      <label class="ld-label">
              Add Project:
            </label>
      <input class="ld-url-input" type="text" name="textdata">
      <input type="submit" name="submit" value="Submit">
    </form>
  </div>
</main>

<div id="super">
  <div id="container">
  </div>
</div>

<script src="https://code.highcharts.com/highcharts.js"></script>
<script src="https://code.highcharts.com/modules/data.js"></script>
<!-- Optional JavaScript -->
<!-- jQuery first, then Popper.js, then Bootstrap JS -->
<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
<script src="./script.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>