var img_names = new Array("teachers", "features", "online_exercises", "contact_us", "view_cart", "buy_now","buybook_now");

function preload_imgs()
{
	for(var loop = 0; loop < img_names.length; loop++)
	{
		var y = new Image();
		y.src = "buttons/" + img_names[loop] + "1.gif";
	}
}

function swap_button(img_num, action)
{
	var x = eval("document." + img_names[img_num]);
	x.src = "buttons/" + img_names[img_num] + action + ".gif";
}