function hideDiv(d) {
document.getElementById(d).style.display = "none";
}
function showDiv(d) {
document.getElementById(d).style.display = "block";
}
var  numInterval = 15000;
function randDiv(){
		window.setInterval('divBanners();', (numInterval + 1500 ));
}
function divBanners(){
var  ran_number = Math.floor(Math.random()*2) + 1; 
	if (ran_number == 1){
  		showDiv('div_1');
		window.setInterval('hideDiv("div_1")', numInterval);
	}
	if (ran_number == 2){
		showDiv('div_2');
		window.setInterval('hideDiv("div_2")', numInterval);
	}
}