function menu_on( menu_item ) {
    if ( document.images ) {
        document[ menu_item ].src = eval( menu_item + "_on.src" );
    }
}

function menu_off( menu_item ) {
    if ( document.images ) {
        document[ menu_item ].src = eval( menu_item + "_off.src" );
    }
}

if ( document.images ) {
    menu_1_on = new Image(); menu_1_on.src="/common/images/menu_1_on.gif";
    menu_1_off = new Image(); menu_1_off.src="/common/images/menu_1_off.gif";
    menu_2_on = new Image(); menu_2_on.src="/common/images/menu_2_on.gif";
    menu_2_off = new Image(); menu_2_off.src="/common/images/menu_2_off.gif";
    menu_3_on = new Image(); menu_3_on.src="/common/images/menu_3_on.gif";
    menu_3_off = new Image(); menu_3_off.src="/common/images/menu_3_off.gif";
    menu_4_on = new Image(); menu_4_on.src="/common/images/menu_4_on.gif";
    menu_4_off = new Image(); menu_4_off.src="/common/images/menu_4_off.gif";
    menu_5_on = new Image(); menu_5_on.src="/common/images/menu_5_on.gif";
    menu_5_off = new Image(); menu_5_off.src="/common/images/menu_5_off.gif";
}