function wheel(event) {

    var delta = 0;

    layertop = parseInt(layer[current_layer].style.top);
    var scrollheight = (document.getElementById('container').offsetHeight - layer[current_layer].offsetHeight);

    if (!event) {
        event = window.event;
    }

    if (event.wheelDelta) {
        delta = event.wheelDelta/120;
        if (window.opera) {
            delta = -delta;
        }
    }

    else if (event.detail) {
        delta = -event.detail/3;
    }

    if (delta) {
        if (delta < 0 && layertop - 1 > scrollheight) {
            layer[current_layer].style.top = layertop - 15 ;
        }
        else if (layertop < -5) {
            layer[current_layer].style.top = layertop + 15;
        }
    }

    if (event.preventDefault)
                event.preventDefault();
        event.returnValue = false;
}



function setsdr() {
    sdr = layer[current_layer].offsetHeight*0.15;
// alert('debug');
}