function changeBanner(option){
	if(option == "previous"){
		var previous = currentBanner-1
		if(previous>0){
			document.getElementById("image_"+currentBanner).style.display = "none";
			document.getElementById("image_"+previous).style.display = "block";
			currentBanner = previous;
		}else{
			document.getElementById("image_"+currentBanner).style.display = "none";
			document.getElementById("image_"+(totalBanners-1)).style.display = "block";
			currentBanner = (totalBanners-1);
		}
	}else{
		var next = currentBanner+1
		if(next<totalBanners){
			document.getElementById("image_"+currentBanner).style.display = "none";
			document.getElementById("image_"+next).style.display = "block";
			currentBanner = next;
		}else{
			document.getElementById("image_"+currentBanner).style.display = "none";
			document.getElementById("image_1").style.display = "block";
			currentBanner = 1;
		}
	}
	
}