为什么此hero图像会覆盖固定导航栏，但在滚动浏览后会重新显示导航栏（） _position

【为什么此hero图像会覆盖固定导航栏，但在滚动浏览后会重新显示导航栏（）】我正在尝试使用HTML和CSS为WordPress构建自定义主题。我遇到的问题是Hero Image似乎总是在固定的顶部导航栏上方-我尝试搜索相似的帖子, 但使用此特定代码集找不到任何内容。向下滚动时, 你会看到固定的导航消失, 然后在英雄图像后重新出现；我最初的倾向是与职位有关(相对/绝对), 但这种变化无济于事。非常感谢任何支持-谢谢！

的HTML

< head> < meta charset="utf-8"/> < meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no"> < meta http-equiv="x-ua-compatible" content="ie=edge"> < title> Designs< /title> < meta name="keywords" content="Designs" /> < meta name="description" content="Designs"> < meta name="copyright" content="Copyright Designs.All rights reserved." /> < meta name="publisher" content="Designs" /> < meta name="author" content="Designs"> < !-- Stylesheets --> < link rel="stylesheet" href="http://www.srcmini.com/stylesheet.css"> < link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css"> < !-- Web Font Pulls --> < link href="https://fonts.googleapis.com/css?family=Lato:300, 400, 400i|Montserrat:400, 700" rel="stylesheet"> < /head> < body> < div class="topnav"> < a class="active" href="http://www.srcmini.com/#home"> Home< /a> < a href="http://www.srcmini.com/#about"> About< /a> < a href="http://www.srcmini.com/#contact"> Experience< /a> < a href="http://www.srcmini.com/#contact"> Projects< /a> < a href="http://www.srcmini.com/#contact"> Musings< /a> < a href="http://www.srcmini.com/#contact"> Contact< /a> < div class="search-container"> < form action="/action_page.php"> < input type="text" placeholder="Search..." name="search"> < button type="submit"> < i class="fa fa-search"> < /i> < /button> < /form> < /div> < /div> < div class="hero-image"> < div class="hero-text"> < h1> This is a hero heading< /h1> < p> Hero sub text< /p> < button> Button< /button> < /div> < /div> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < h1> My First Heading< /h1> < p> My first paragraph.< /p> < /body>

的CSS

body { background-color: powderblue; } h1 { color: blue; } p { color: red; } {box-sizing: border-box; } body { margin: 0; font-family: Arial, Helvetica, sans-serif; } .topnav { overflow: hidden; background-color: #e9e9e9; position: fixed; top: 0; width: 100%; } .topnav a { float: left; display: block; color: black; text-align: center; padding: 14px 16px; text-decoration: none; font-size: 17px; } .topnav a:hover { background-color: #ddd; color: black; } .topnav a.active { background-color: #2196F3; color: white; } .topnav .search-container { float: right; } .topnav input[type=text] { padding: 6px; margin-top: 8px; font-size: 17px; border: none; } .topnav .search-container button { float: right; padding: 6px 10px; margin-top: 8px; margin-right: 16px; background: #ddd; font-size: 17px; border: none; cursor: pointer; }.topnav .search-container button:hover { background: #ccc; }@media screen and (max-width: 600px) { .topnav .search-container { float: none; } .topnav a, .topnav input[type=text], .topnav .search-container button { float: none; display: block; text-align: left; width: 100%; margin: 0; padding: 14px; } .topnav input[type=text] { border: 1px solid #ccc; } } body, html { height: 100%; }body, html { height: 100%; margin: 0; }.hero-image { background-image: url("https://static.pexels.com/photos/440731/pexels-photo-440731.jpeg"); height: 50%; background-position: center; background-repeat: no-repeat; background-size: cover; position: relative; }.hero-text { text-align: center; position: absolute; top: 50%; left: 50%; transform: translate(-50%, -50%); color: white; }.hero-text button { border: none; outline: 0; display: inline-block; padding: 10px 25px; color: black; background-color: #ddd; text-align: center; cursor: pointer; }.hero-text button:hover { background-color: #555; color: white; }

#1你是否尝试过将z-index：999添加到.topnav。
#2你只需要添加一个z-index：