【relation】
<!DOCTYPE html>
<html>
<head>
<style type='text/css'>
.demo span span { /* No nested span */
color: red;
}
.demo2 span+span { /* Selects span adjacent to another span */
color: red;
}
</style>
</head>
<body>
<div class="demo">
<span>1</span> <span>2</span>
</div>
<div class="demo2">
<span>1</span> <span>2</span>
</div>
</body>
</html>
