// changes image of button to hover image
function hover_button(nav_button_img) {
	var img = nav_button_img;
	img.src = "/images/navbar_" + img.id + "_hover.png";
}

// sets original button image
function normal_button(nav_button_img) {
	var img = nav_button_img;
	img.src = "/images/navbar_" + img.id + ".png";
}