<!DOCTYPE html>
<html>
<head>
<title>Title of the document</title>
<style>
.gradient {
height: 300px;
background-color: blue;
background-image: linear-gradient(to left, #f50707, #f56e00,#f7df00, #66f507, #0052b0, #520f41, #ff0856);
}
</style>
</head>
<body>
<div class="gradient"></div>
</body>
</html>