function setBgImg() {
	// ランダムに画像を表示する
	img = new Array();
	img[0] = "images/top01.jpg";
	img[1] = "images/top02.jpg";
	img[2] = "images/top03.jpg";
	img[3] = "images/top04.jpg";
	img[4] = "images/top05.jpg";
	n = Math.floor(Math.random()*img.length);
	document.getElementById("contentsArea").style.backgroundImage = 'url('+img[n]+')';
}//</setBgImg>

window.onload = function() {
  setBgImg();
};