var curNav = 'nav0';

function setCurNav(newNav, imgOn, imgOff) { 
	if(document.getElementById(curNav)) {
		document.getElementById(curNav).style.backgroundImage = 'url('+imgOff+')'
	}
	if(document.getElementById(newNav)) {
		document.getElementById(newNav).style.backgroundImage = 'url('+imgOn+')';
	}
	curNav = newNav;
}