var wall = new Array();

wall[0] = "http://navi.nihonbashi.ac.jp/images/index.jpg";
wall[1] = "http://navi.nihonbashi.ac.jp/images/index2.jpg";
wall[2] = "http://navi.nihonbashi.ac.jp/images/index3.jpg";
wall[3] = "http://navi.nihonbashi.ac.jp/images/index4.jpg";
wall[4] = "http://navi.nihonbashi.ac.jp/images/index5.jpg";
wall[5] = "http://navi.nihonbashi.ac.jp/images/index6.jpg";

var rnd = Math.floor((Math.random() * 100)) % wall.length;
document.write('<style type="text/css">#naviIndex { background-image:url(' , wall[rnd] , '); }</style>');

function menu(obj){
	if(document.getElementById){
		document.getElementById(obj).style.display=='none'?document.getElementById(obj).style.display='':document.getElementById(obj).style.display='none'
		}
	else if(document.all){
		document.all(obj).style.display=='none'?document.all(obj).style.display='':document.all(obj).style.display='none'
		}
	else if(document.layers){
		document.layers[obj].display=='none'?document.layers[obj].display='':document.layers[obj].display='none'
		}
}