function menu_switch (id){
	blt_img = "image/bullet";
	blt_ext = ".gif";
	menuDiv = document.getElementById (id);
	menuBlt = document.getElementById (id + "_blt");
	if (menuDiv.style.display == "block"){
		menuDiv.style.display = "none";
		menuBlt.src = blt_img + blt_ext;
	} else {
		menuDiv.style.display = "block";
		menuBlt.src = blt_img + "_act" + blt_ext;
	}
}