Devils advocate Yes they can.
Try this:
<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>Untitled Document</title>
<style>
div{display:inline;background:blue;padding:25px 0}
div + div{display:block;background:red;}
</style>
</head>
<body>
<div>one</div>
<div>two</div>
</body>
</html>