function randomHeader() {
	var Display = document.getElementById('top');
	var randomnumber=Math.floor(Math.random()*4)

	switch (randomnumber)
	{
		case 0:
			Display.style.background = "url(http://www.thefis.com/images/background-04.jpg) 0px center no-repeat";
			break;
		case 1:
			Display.style.background = "url(http://www.thefis.com/images/background-05.jpg) 0px center no-repeat";
			break;
		case 2:
			Display.style.background = "url(http://www.thefis.com/images/background-06.jpg) 0px center no-repeat";
			break;
		case 3:
			Display.style.background = "url(http://www.thefis.com/images/background-07.jpg) 0px center no-repeat";
			break;
	}
}