curmenu = 0;

function showmenu(clkmenu) {
	var damenu = "";
	var x;

	//first, hide all menus:
	for (x=1; x<8; x++) {
		damenu = "submenu" + x;
		document.getElementById(damenu).style.visibility = "hidden";
		document.getElementById(damenu).style.display = "none";
	}
 
	//show chosen menu:
	damenu = "submenu" + clkmenu;
	if (clkmenu != curmenu) {
		document.getElementById(damenu).style.visibility = "visible";
		document.getElementById(damenu).style.display = "block";
		curmenu = clkmenu;
	} else {
		//hide the menu if clicked a second time
		document.getElementById(damenu).style.visibility = "hidden";
		curmenu = 0;
	}
}