function ops4_menu_switch_on ( num ) {
	Element.hide ( 'ops4_menu_switch_on_'+num );
	Element.show ( 'ops4_menu_switch_off_'+num );
	new Effect.BlindDown ( 'ops4_menu_content_'+num, {duration:0.5} );
}

function ops4_menu_switch_off ( num ) {
	Element.hide ( 'ops4_menu_switch_off_'+num );
	Element.show ( 'ops4_menu_switch_on_'+num );
	new Effect.BlindUp ( 'ops4_menu_content_'+num, {duration:0.5} );
}

function add_onload_function(func) {
  var oldonload = window.onload;
  if (typeof window.onload != 'function') {
    window.onload = func;
  } else {
    window.onload = function() {
      oldonload();
      func();
    }
  }
}