function showMenu ( menu_id, link_id ) {
	document.getElementById(menu_id).style.display = 'block';
	document.getElementById(link_id).className = 'menu_div over';
}
function hideMenu ( menu_id, link_id ) {
	document.getElementById(menu_id).style.display = 'none';
	document.getElementById(link_id).className = 'menu_div';
}