function turnOn (element) {

	var theImage = eval('document.' + element);
	var newSource = '../../../images/nav_' + element + '_on.gif';
	theImage.src = newSource;

}

function turnOff (element) {

	var theImage = eval('document.' + element);
	var newSource = '../../../images/nav_' + element + '_off.gif';
	theImage.src = newSource;

}