// preload images
function navImage(name, width, has_picture)	{
	var off_src = 'resources/images/buttons/' + name + '_off.gif';
	var ovr_src = 'resources/images/buttons/' + name + '_over.gif';
	var height = 15;
	this.button_off = new Image(width, height);
	this.button_off.src = off_src;
	this.button_over = new Image(width, height);
	this.button_over.src = ovr_src;
	this.has_picture = has_picture;
	return this;
}

function over(name)	{
	if(document.images)	{
		var navimg = navigation[name];
		document.images[name + '_btn'].src = navimg.button_over.src;
		if(navimg.has_picture)	{
			document.images[name + '_pic'].style.borderColor = '#EEE4B1';
		}
	}
}
function off(name)	{
	if(document.images)	{
		var navimg = navigation[name];
		document.images[name + '_btn'].src = navimg.button_off.src;
		if(navimg.has_picture)	{
			document.images[name + '_pic'].style.borderColor = 'black';
		}
	}
}