function randomMain () {
	var imgArray = new Array ();
	imgArray[0]					= "img/top01.jpg";
	imgArray[imgArray.length]	= "img/top02.jpg";
	imgArray[imgArray.length]	= "img/top03.jpg";
	imgArray[imgArray.length]	= "img/top04.jpg";
	imgArray[imgArray.length]	= "img/top05.jpg";
	imgArray[imgArray.length]	= "img/top06.jpg";
	imgArray[imgArray.length]	= "img/top07.jpg";
	imgArray[imgArray.length]	= "img/top08.jpg";
	var randomNum = Math.floor(Math.random() * imgArray.length);
	document.mainImg.src = imgArray[randomNum];
}