var img_arrow_d = "img/arrow_red_d.gif";
var img_arrow_l = "img/arrow_red_l.gif";

function flipDisplay(img, id) {
    var obj = document.getElementById(id);
    if(obj.style.display == "none") {
        obj.style.display = "block";
        img.src = img_arrow_d;
    }
    else { 
        obj.style.display = "none";
         img.src = img_arrow_l;
    }   
}