//文字コードはUTF-8N
//背景設定
function rnd_bg(){
	var img_no=Math.floor(Math.random()*8+1); //1~8を取得
	var setbg='entrance/bg0'+img_no+'.jpg';
	document.body.style.backgroundImage = "url(" + setbg + ")";
	document.body.style.backgroundRepeat = 'no-repeat';   
	document.body.style.backgroundPosition = 'center';   
	document.body.style.backgroundColor = '#000000';   
}