function button(i, state) {
	var bsrc = i.src;     
	if (bsrc)    
	{
	   	i.src = bsrc.replace(i.state, state);
		i.state = state; 
	}
}

function initNav() {

	// get all of the buttons
	// var buttons = document.getElementsByClassName('button');
	var buttons = $('nav').getElements('img.button');   
	for(var b in buttons) {
		// set default state
		buttons[b].state = '/up/';
		buttons[b].onmouseover = function () {
			button(this, '/ro/');
		};
		buttons[b].onmouseout = function () {
			button(this, '/up/');
		};
		buttons[b].onmousedown = function () {
			button(this, '/dn/');
		};
		buttons[b].onmouseup = function () {
			button(this, '/up/');
		};
	}
	var buttons = $('nav').getElements('img.sel');
	for(var b in buttons) {
		// set default state
		buttons[b].state = '/up/';
		button(buttons[b], '/dn/');
		buttons[b].onmouseover = function() {};			
		buttons[b].onmouseout = function() {};
		buttons[b].onmousedown = function() {};
		buttons[b].onmouseup = function() {};
	}
}