var tabcount = 2;
				function notice_chart_view(num){
					for (i=1; i<=tabcount; ++i) {
						var notice_chart = document.getElementById("notice_chart" + i);
						if (i == num) {
							notice_chart.style.display="";
						} else {
							notice_chart.style.display="none";
						}
					}	
                       		}
				var visible_tab = Math.floor((Math.random() * (tabcount - 0.1))) + 1;
				notice_chart_view(visible_tab);