<html>
<head>
<style type="text/css">
.c1 { color: red; }
.c2 { background: blue; }
#i1 { color: green; }
</style>
</head>
<body>
<div>
<div id='i1'>Hello</div>
<div class='c1'>World</div>
<div class='c2'>Hello</div>
<div class='c1 c2'>World</div>
</div>
</body>
</html>