<html>
<head>
<style>
#grad1 {
height: 200px;
background-image: linear-gradient(to right, red, orange, yellow, green, blue, indigo, violet);
}
</style>
</head>
<body>
<h1>Linear Gradient - Rainbow effect</h1>
<div id="grad1" style="text-align:center;margin:auto;color:#888888;font-size:40px;font-weight:bold">
Gradient Background
</div>
</body>
</html>