var promononURL = "imgs/promonon1.jpg";

if (document.images) {
     var promonon1 = new Image();
     promonon1.src = "imgs/promonon1.jpg";

     var promonon2 = new Image();
     promonon2.src = "imgs/promonon2.jpg";
	 
	 var promonon3 = new Image();
	 promonon3.src = "imgs/promonon3.jpg";
	 
	 var promonon4 = new Image();
	 promonon4.src = "imgs/promonon4.jpg";
	 
	 var catalog = new Image();
	 catalog.src = "imgs/catalog.jpg"
	 
}

function changePromonon() {
	if (document.images) {
		if (promononURL == "imgs/promonon1.jpg") promononURL = "imgs/promonon2.jpg";
		else if (promononURL == "imgs/promonon2.jpg") promononURL = "imgs/promonon3.jpg";
		else if (promononURL == "imgs/promonon3.jpg") promononURL = "imgs/promonon4.jpg";
		else if (promononURL == "imgs/promonon4.jpg") promononURL = "imgs/catalog.jpg";
		else if (promononURL == "imgs/catalog.jpg") promononURL = "imgs/promonon1.jpg";
		
         document.myPromonon.src = promononURL;
	}
}

function changePromononBack() {
	if (document.images) {
		if (promononURL == "imgs/promonon1.jpg") promononURL = "imgs/catalog.jpg";
		else if (promononURL == "imgs/promonon2.jpg") promononURL = "imgs/promonon1.jpg";
		else if (promononURL == "imgs/promonon3.jpg") promononURL = "imgs/promonon2.jpg";
		else if (promononURL == "imgs/promonon4.jpg") promononURL = "imgs/promonon3.jpg";
		else if (promononURL == "imgs/catalog.jpg") promononURL = "imgs/promonon4.jpg";
		
         document.myPromonon.src = promononURL;
	}
}