function tab_click(tab_on_id, tab_content_on_id, tabs_selector_arg, tab_content_selector_arg) {
  var tabs_selector = tabs_selector_arg || "div.tab-holder li.active";
  var tabs_content_selector = tab_content_selector_arg || "div.tab-content div.active";
  
  $S(tabs_selector).each( function (tab) {tab.className = '';});
  $(tab_on_id).className = 'active';

  $S(tabs_content_selector).each( function (tab_content) {tab_content.className = 'inactive';});
  $(tab_content_on_id).className = 'active';
  
}