var bgNumber=2;
var bgMax=6;

function alteraImagem(baseDir) {
	
	bgNumber = bgNumber + 1;
	
	if(bgNumber > 6) bgNumber=1;
	
	if(document.body) {
		
		document.body.background = baseDir+"imagens/design/bgprincipal/bg" + bgNumber + ".jpg";
	}
}