<!DOCTYPE html>
<html>
<head>
<style>
.classname {
background-color: green;
color: white;
}
#idname {
background-color: pink;
color: white;
}
</style>
</head>
<body>
<div class="classname">I am green colour<div>
<div id="idname">I am pink colour</div>
</body>
</html>