var couter = 1;

function swap_class() {
	var elm = document.getElementById('home');
	if(elm) {
		switch(elm.className) {
			case 'bg1':
				elm.className = 'bg2';
				break
			case 'bg2':
				elm.className = 'bg3';
				break
			case 'bg3':
				elm.className = 'bg1';
				break
		}
	}
	start_timer();
}

function start_timer() {
	// 1 sec = 1000 ms
	setTimeout("swap_class()", 5000);
}

start_timer();