linear-gradient-ref.html
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<style>
#gradient {
width: 400px;
height: 300px;
background-image: linear-gradient(to right, black 0%, red 50%, gold 100%);
}
</style>
</head>
<body>
<div id="gradient"></div>
</body>
</html>