I actually had this problem (before I knew about StackOverflow).
Your code is (mostly) fine.
The problem is the computer doesn't know what to do.
A div is simply a divider. (Pretty sure that div is a abbreviated version of divider).
A divider without anything inside it is empty. Useless.
You need to put something in it to apply color, size, ect.
See the following Stack Snippets®.
As you can see, adding text is a simple way to solve your problem.
.header {
background-color: #111111;
}
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="designs.css">
</head>
<body>
<div class="header">
And look at that. Problem solved.
</div>
</body>
</html>
If you don't want text, add a <br>
.
.header {
background-color: #111111;
}
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="designs.css">
</head>
<body>
<div class="header">
<br>
</div>
</body>
</html>
You can even set the size of the div, too!
.header {
height: 200px;
width: 50 px;
background-color: #111111;
}
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="designs.css">
</head>
<body>
<div class="header">
Some text here whose div has been set to 200 by 50 px
</div>
</body>
</html>