var old="";
function tabmenu(tab_name, img_url)
{
	submenu = eval(tab_name + ".style");
	if(old != submenu)
	{
		if(old != "")
		{
			old.display = "none";
		}
	}
	submenu.display = "block";
	old = submenu;
	document.tabmenu.src = img_url;
}