function tab_click (url)
{
        window.location = url;
}
function tab_mouseover (tab, x, y)
{
        tab.style.backgroundPosition = x+"px "+y+"px";
}
function tab_mouseout (tab, x, y)
{
        tab.style.backgroundPosition = x+"px "+y+"px";
}
function flip_bg_img (obj, img)
{
        obj.style.backgroundImage = "url("+img+")";
}