function show_menu(item) {
	item_name = item.src.split('menu_')[1];
	item_name = item_name.split('.')[0];
	item_name = item_name.split('_')[0];

	hide_menu(item_name);

	item.src = '/images/menu_' + item_name + '_over.jpg';
	sub_menu_id = document.getElementById('sub_menu_' + item_name);
	if(sub_menu_id.innerHTML != '') {
		sub_menu_id.style.display = 'block';
	}
}

function hide_menu(item_name) {
	items = new Array('main', 'about', 'students', 'companies', 'report');
	for(var i = 0; i < items.length; i++) {
		if(item_name != items[i] && item_name != undefined) {
			sub_menu_id = document.getElementById('sub_menu_' + items[i]);
			sub_menu_id.style.display = 'none';

			menu_id = document.getElementById('menu_' + items[i]);
			menu_id.src = '/images/menu_' + items[i] + '.jpg';
		}
	}
}