Image1 = "url(/images/back_predmenu1.jpg)";
Image2 = "url(/images/back_predmenu2.jpg)";

function ZapniMenu(menu_id) {
    if (menu_id == 1) {
        document.getElementById('predmenu').style.backgroundImage = Image1;
        document.getElementById('predmenu_2').style.color = "#fff";
        document.getElementById('predmenu_1').style.color = "yellow";
        document.getElementById('menu_2').style.display = 'none';
        document.getElementById('menu_1').style.display = 'block';
    } else {
        document.getElementById('predmenu').style.backgroundImage = Image2;
        document.getElementById('predmenu_1').style.color = "#fff";
        document.getElementById('predmenu_2').style.color = "yellow";
        document.getElementById('menu_1').style.display = 'none';
        document.getElementById('menu_2').style.display = 'block';
    }
    return false;
}