function toggle(submenu) {
    if (document.getElementById(submenu).style.display == 'none') {
        document.getElementById(submenu).style.display = 'block';
		  document.getElementById('articles').style.listStyleImage = 'url(/images/minus.gif)';
    } else {
        document.getElementById(submenu).style.display = 'none';
		  document.getElementById('articles').style.listStyleImage = 'url(/images/plus.gif)';
    }
}