body {
margin: 0;
font-family: 'Raleway', sans-serif;
font-size: 14px;
color: #6c7279;
-webkit-font-smoothing: antialiased;
background-color: #000;
}
*,
*:before,
*:after {
box-sizing: border-box;
}
/* Container
===================*/
.container {
width: 100%;
max-width: 1170px;
margin: 0 auto;
}
/* Header
===================*/
.header {
padding: 38px;
position: absolute;
top: 0;
left: 0;
z-index: 1000;
width: 100%;
}
.header__inner {
display: flex;
justify-content: space-between;
border-bottom: 1px solid #515369;
padding: 38px;
align-items: center;
}
.nav {
font-size: 13px;
font-weight: 700;
text-transform: uppercase;
display: flex;
}
.nav__link {
color: #fff;
text-decoration: none;
opacity: 0.75;
transition: opacity .2s;
margin-left: 53px;
}
.nav__link:hover {
opacity: 1;
}
/* Intro
===================*/
.intro {
height: 750px;
background: #31344e url(img/intro-bg.jpg) center no-repeat;
background-size: cover;
}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<link href="https://fonts.googleapis.com/css?family=Cardo:400i|Open+Sans:700|Raleway:400,600,700&display=swap" rel="stylesheet">
<link rel="stylesheet" href="css/style.css">
<title>Мой сайт</title>
</head>
<header class="header">
<div class="container">
<div class="header__inner">
<div class="header__logo">
<img src="img/ActiveBoxlogo.png" alt="">
</div>
<nav class="nav">
<a class="nav__link" href="#">Features</a>
<a class="nav__link" href="#">Works</a>
<a class="nav__link" href="#">Our Team</a>
<a class="nav__link" href="#">Testimonials</a>
<a class="nav__link" href="#">Download</a>
</nav>
</div>
</div>
</header>
<div class="intro"></div>
</body>
</html>
你的路径不正确。由于css文件不在根目录下,而是在文件夹下,所以需要先退出到根目录,然后再去img: