<!DOCTYPE html>
<html>
<head>
  <script src="jquery-1.4.2.js"></script>
</head>
<body>
	<button>Toggle</button>
<p>GOOD DAY</p>
<p style="display: none">GOOD NIGHT</p>
<script>

var flip = 0;
$("button").click(function () {
$("p").toggle( flip++ % 2 == 0 );
});
</script>
</body>
</html>